How to DEBUG Pine Script Code

good day Traders welcome back to another
video on our favorite language Pine
script in today's video we're going to
be dealing with a subject that's not
particularly sexy but it is very
important for us to understand and that
is the subject of debugging our scripts
for those who aren't aware of the term
debugging it basically just means
looking under the hood of our script and
seeing what the script is actually doing
for example if we're working with a for
Loop and our script is giving us
incorrect output then we may want to
look inside the for Loop and see what
each Loop is doing and that's what I
have on my chart here we have two labels
here that is essentially debugging a for
Loop now there are multiple ways to
debug our scripts there are multiple
reasons why we might want to and in
today's lesson we're going to cover all
of those but before we do that I just
want to really quickly make you guys
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way let's get into today's lesson all
right so to get started here I just have
a simple script that's plotting the
closing price of the market that we're
on Market is irrelevant but we're on
bitcoin for now and we're plotting a
horizontal line at 20,000 this is just
to set the chart scale and I'll explain
why in a moment so I open up my code
here we're just plotting the close price
and we're giving the plot a title um you
could also specify this um but if you're
not aware in pin script you need to put
the parameters in order of their
appearance in the documentation so the
first thing we're plotting is a series
in this case it's the closing price
series the second parameter is a title
so I can have a string Title Here the
third parameter is a color so if I put
them in order I don't need to specify
what the parameter is but if they're not
in order like
this then the script won't compile
because these parameters are not in the
correct position and so what I would
need to do here if I
wanted to put the parameters in any
order I need to specify what the
parameters are so we have a plot here
that's plotting the closing price color
of blue and the title closing price so
now if I come up to the data window
which is this button here and I click on
that here is the date and time of the
market we're on here is the uh Market's
price data volume and um open high low
close and then here is our script that
we've added to the Chart so this data
window will list all of the indicators
you have added to your chart and when
we're developing a script this is where
we can start to debug our values so if I
hover my mouse over past bars here
you'll see this closing price data value
updating so this is the first
introduction to debugging your scripts
obviously you can also just look at the
plot here but if you've got several
plots drawing out on your indicator it
can get really confusing knowing which
one's which so that's where the data
window comes in handy we can see the
title of each value that we're drawing
so now that we have our chart scale set
let's create some debugging values some
values we can work with so for today's
video I'm going to just work with volume
average volume so what we're doing here
is we're getting the average volume over
the past 50 bars using an SMA simple
moving average or smooth moving average
so we're calculating the 50 period SMA
of volume and that gives us our average
volume then we have a Boolean value here
a true false value that checks if the
the current bars volume is greater than
the average volume over the past 50 bars
so now if we wanted to debug the raised
volume Boolean value and see if it's
true or false on each bar on our chart
we can use the plot function for this
however if I just try to plot raised uh
volume as a plot like this my script
won't compile because this is a Boolean
value not a number and plot can only
plot numbers so what we would need to do
here instead is use a conditional
operator so we can say is raised volume
true question mark If if so plot one
otherwise plot zero now when I save my
script we'll be getting ones and zeros
drawing up here to let us know whether
or not volume is raised above the moving
average I can also title this uh raised
volume and now this plot is showing up
in my data window however if I minimize
this uh script you can see that our
chart scaling is now all screwed up so
we're plotting 0 and one all the way
down here we're also plotting the price
value and because we're plotting one or
zero the chart will automatically scale
to show all the plots in your script and
so that screws up our our chart scaling
the way we can get around this and still
plot this one and zero debug value to
the data window is using the plot Char
function or car plot character this is
short for plot character to the chart
and it's similar to the plot function in
that it takes a series however it also
takes a character and so what we can do
here is I can just get rid of title
since we're inputting all these
parameters in order I can plot our
series our title the character is just
going to be blank and we can leave it as
that and if I save my code the chart
scale here will be corrected see now it
is um automatically scaling because I'm
on auto here if you look really closely
it's hard to see but there's these
little blue dots all over the place
those are our plot character functions
plotting a blank character I don't know
why it plots a DOT instead of a blank
character which is what we wanted but
it's an easy thing to fix all we need to
do is specify the color of our uh plot
Char function and it doesn't matter what
color you set this to because we're
going to set the colors transparency to
100% so I could set this to color. new
color. red 100 and now what you'll see
is this number here will turn red and
all of those little blue dots on my
chart will disappear so keep an eye on
these two things there we go our raise
volume is now red and we are not getting
anything drawing on the chart you can do
the same thing with regular plots but
again remember that will screw up your
chart scaling in many circumstances so
that's one way to debug Boolean values
another way my preferred method when I'm
developing a script just because it's
really quick and easy um and very I'm a
very visual Trader so just staring at a
bunch of numbers will often just make my
brain switch off so I like to use things
like changing the background color of my
chart based on a condition when I'm
developing my script once I've built my
script maybe I'll change that background
color into a plot shape something that
looks a little bit better a little bit
more tidy but when I'm developing and I
want to get my code written quickly I'll
just use the BG color function to check
is raise volume true if so set the
background color of my chart to color do
green with 50% transparency otherwise
set my background color to nothing now
if I save my code I can close a data
window and I can just see when volume is
raised by this background color here now
it looks terrible obviously so when you
finish your script as I said you might
want to turn this into a plot shape
function that draws boxes at the bottom
of your indicator or something like that
but for now this will do it's a very
quick method for debugging uh
particularly market conditions and just
general true false values so that's the
beginning of debugging now the next
thing I was going to show you which I
already have shown you is the plot Char
difference so let me copy some code over
here and explain what's happening
displaying data in the data window is
achieved using plots so plots do work
plot shapes also work uh that will show
up in the in the data window however the
preferred option is plot Char as I
mentioned because it will not affect
your chart scale so now if I save my
code we won't be drawing raise volume
anymore but now we're plotting out
average volume so we can actually see
what our average volume is and if I copy
this code uh and paste underneath here
volume I can say current
volume now we can compare the average
volume to the current volume and so if
you look at when I hover over a green
bar current volume is going to be higher
than average volume that's the condition
that sets our background color of our
chart to Green but just to reiterate for
those who are new to Pine scripts if I
were to plot the number one onto my
chart that's going to jack up my chart
scaling cuz now we're plotting one all
the way up to the current uh market
price price which is 22,000 so the
correct method is to use plot so that
covers the majority of circumstances
where you might want to debug your
script obviously this is a super simple
script but if you're working with dozens
of different values you can use the plot
Shar function to see what they're all
doing and sort of break down the inner
workings of your script and see under
the hood see what all of your uh
variables are by hovering over each bar
on your chart and you can double check
and confirm that your script is doing
what you think it's doing however when
we're working with for Loops things get
a little bit more complicated because if
I write out a simple for Loop here we
can't say plot Char uh the current bars
volume in our for Loop uh say
volume with a blank character if I save
my code here we're going to get an error
because we cannot use any plot functions
inside a local scope so that means we
cannot use it in an if statement uh
anything that's tabbed this is a local
scope of our for Loop we cannot use any
plots anything to draw to the Chart
inside a scope so we can't draw in for
Loops we can't draw an if statements we
can't draw in functions we can only draw
in the main scope of our script so if we
want to see what our for Loop is doing
on each Loop things are a little bit
more complicated for today's example to
keep things really simple let's just add
up the bar size of the past 10 bars uh
technically this would be the past 11
bars cuz we're starting from Z counting
up to 10 if you wanted to do the past 10
bars this would be 0 to 9 and that would
start counting from the current bar zero
back 0 1 2 3 4 5 6 7 8 9 which would be
10 bars so I'll leave it as that for now
let's count back the pass 10 bars and
what we're going to do is we're going to
add up the total bar size over that look
back period to do that I just need to
add or or update the total bar size to
whatever its current value is on it on
this current Loop plus the current bars
High the current bar in our Loop so I is
the bar index of our Loop so the high
minus the low of this current Loop and
then I can use a plot Char to plot what
our total bar size is so now if I saved
my code uh this is incorrect let me
change that to Total bar size so now we
can see that the total bar size adding
up the bar size of past 10 bars on our
chart gives us 26 132 and now if I were
to divide this number by 10 that would
give us the average bar size over the
past 10 bars let's do that next I can
say average bar size equals total bar
size / 10 now if I wanted to turn this
into a user input I could say uh loop
length equals input.
integer uh look back we give it a
default value of 10 and I I've been
getting into a new habit of declaring
what my data type type is when I declare
a variable you don't have to do this
pinescript will automatically detect
what type of uh what data type you're
working with but I've started to do this
because with the new latest Pine editor
the color coding makes it a lot easier
to read your code and see what each
variable is so anyway here's that Loop
length um When We're looping remember
zero counts as one so what we need to do
here is subtract one from our uh Lo back
length and then when I'm dividing my
average bar size I need to paste that
Loop length in there with subtracting
one from it and now we're looping from 0
to 9 technically 10 bars and then
dividing the total bar size by our look
back length now if I save my code well
actually I forgot to plot this hang on
um let's plot the average bar size I'll
put this under our bar size I think
that'll make it more intuitive to read
the data window so now when my script
compiles we have the total bar size over
the past 10 bars and we have the average
bar size over those 10 bars and if I
wanted to I could also uh add in our
look back length and paste that in there
and so now all these red numbers are
showing us our look back period the
total bar size over that look back
period and the average bar size over
that look back period however what if we
were doing something more complicated
within this for Loop and our script was
giving incorrect output and we didn't
know why that's where debugging the for
Loop comes into play and the best way to
do this there are multiple ways you
could create an array and you could feed
each value into into the array and plot
them all individually using plot chars
that's an option but it's a little bit
convoluted my preferred option is to
Simply do what's referred to as building
a string so we can build a string a
string of text that adds the for Loop
values to the text and then at the end
of our for Loop we can draw a label onto
our chart that shows what happened
within the for Loop during each Loop so
to do that I'm going to create a new
variable here called string debug string
and it's going to start out as just a
blank string with nothing in it and then
what we're going to do is we're going to
build our string so the same way we add
up our total bar size by assigning total
bar size to Total bar size plus the
latest Loop value we do the same thing
with our debug
string so we're going to set debug
string to whatever it currently is plus
and then I'm going to uh this is going
to get a little bit complicated to read
but it's really quite simple what we're
going to do here is we're going to open
a square bracket and then add the
current Loop index I to this string so
that we know what this string is
referring to but remember when we're
dealing with pin script we cannot add a
number to a string directly we need to
use the Str str. TW string function to
convert the number into text so that our
script will compile and now if I closed
that bracket off and I add a back sln
this back sln will create a new line and
then when we draw this string onto a
label uh each Loop value will be on its
own line and it'll make it easy to read
so now that we have our debug string
we'll expand on this in a moment but
just so that we are all on the same page
let's first simply draw this debug
string to the chart using a label so to
do that I'm going to check if the
current bar state is the last last bar
on my chart if I don't do this and we
just draw label on every bar then we'll
have labels all over the place and it
will be really hard to read so what we
want to do is only draw the label on the
final bar and then we can debug the
latest 10 bars to make sure that our
script is doing what we hope it is so to
create a new label I can say label. new
and then we need to pass in the bar
index and a price value so for this
label I'll set it to the current bars
high now we need to specify the text for
the label that's just going to be our
debug
string and I'm also going to set the
color to color. Black and the text color
to color. white and one final thing I'm
going to do to make our label easy to
read is set the text align to left cuz I
think by default it's centered and so if
we have an inconsistent string length um
it'll Center everything and it's just
not ideal we want everything to be
aligned to the left that that'll make it
easy to read so I can set text align
equals text. align left and let's hide
the data window so we can see more code
here so now when I save my code keep an
eye on this label here there we have
it so we are now building a string and
each string starts with the loop index
and then what we can do here is we can
start adding uh values from within our
Loop so for example uh we could say here
total bar size equals plus Str str2
string total bar size and then I need to
finish that string and now if I save my
code we'll be getting more information
on this label there we go so on the very
first loop on the very first bar on our
chart the total bar size is 155 and we
can verify that by measuring the bar and
close enough 155 so this is an accurate
value then we can check Loop number one
which is this uh next bar back the bar
size there is 312 so now if I measure
from the high down to the low uh 155 +
169 is approximately 312 so remember
we're adding up the bar sizes as we loop
back if we wanted to see what the bar
size of each bar is on our Loop we need
to change our code a little bit here and
to make this easier to read this isn't
necessary you can just keep writing the
string off the screen if you want to but
since I'm doing this for YouTube uh I'm
going to start a new line here and to
start a new line when you're dealing
with a single uh expression in pin
script this here is an expression if I
want to extend this expression to
multiple lines then I need to press
enter here then tab and then one space I
don't know why but that's how Pine
script works if I don't have this space
here my script will not compile but if I
add a space after that tab it will
compile I think you can also just have
one space here that works too so
whatever makes more sense to you
personally I find the tab in one space
makes more sense to me because it's more
obvious that I'm extending this line um
sometimes it might be hard to see this
single space but it's just a matter of
preference just make sure that you have
one space after you start your new line
and you're at least on the same scope as
our expression so now what I can do is
uh I'll actually bring this one back and
we'll start a new string here uh we need
to have a space here because otherwise
this will add on to the end of this
number so one space and then I can say
bar size equals and then Str str2 string
High minus low of our current
Loop and then now if I Sav my code we
should be getting more information so
now it's showing the bar size of each
bar as we loop back and it's showing the
total bar size as that is being
accumulated so you can see now how this
can really help us get an insight into
what our for Loops are doing and that's
really it I mean we could add more
information here if we want to so for
example I could start a third line here
and I could specify or
display the current bars high price and
the current bars low price and when I
say current bar I mean the current bar
in our Loop uh so when I save my code
now we're getting a lot more information
we're getting the total bar size the
current bar size the current bars High
the current bars low and the
corresponding looping index for that
information and so now we can double
check that our script is actually
working with the same data that we want
it to and it's outputting the correct
information and that's it that's really
it for pinescript debugging
unfortunately there's no better way to
do this sort of thing I wish the data
window had an option for plotting things
that do not draw onto your indicator
values uh any plots even plot chars that
are blank and aren't drawn onto your
indicator we'll have a number here in
the indicator values list I wish there
was a way to hide these so that you
could only see them in the data window
that would make some scripts a lot
tidier especially ones that have tons of
plots like my ultimate pullback
indicator that I showed you guys in the
previous video that has tons of plots
and these numbers just go off the chart
and it just clutters up your screen
obviously you can come into the settings
menu and you can turn off indicator
values and then they're all gone uh but
sometimes you want to know what those
indicator values are without opening the
data window but anyway I digress I also
wish there was a way to um send text
directly to the console here that would
make things so much easier for us as
Pines scrips if we could just say um
print and
then some sort of text and that would
come into the console that would be a
super useful feature in pinescript but
unfortunately for whatever reason we do
not have that capability yet and so the
next best thing is just using labels and
so before I wrap up this lesson let's
first of all set overl to True here and
I'll remove this script and add it back
to my chart so that we're drawing over
actual price action and the final thing
I want to show you guys is how to debug
a specific bar so this is debugging the
latest bar the last bar on our chart but
what if we wanted to go back around here
somewhere and analyze this bar here well
there is one method for doing this that
is pretty convenient and that is using a
user input that sets a bar time and then
if you set that user input to confirm uh
I'll show you what that means in a
moment if confirm is true on that user
input then you can click on the bar
itself and tell your script where to
start drawing something like a label
from so to wrap up this lesson let me
show you how to do this I'll just paste
over some code to save time so this time
we're using a confirm time input to
display a label on the selected bar so
we're getting an in integer bar type
time which is a Unix timestamp you don't
need to know what that means but it's
basically just a timestamp it allows you
to specify a time as an integer simple
integer that will tell our script where
we want to draw something so in this
case we're using the input. time
function the default value will be NE -1
and we have set confirm equals true and
what this will mean is when we um add
the script to our chart for the first
time we will need to use our Mouse to
select a bar so now I can pretty much
copy this line of code here to check if
we're on the last bar on our chart and
then I can say and bar time is not equal
to -1 that means that the user has
selected a bar time if a user has
selected a bar time then we want to draw
our label on the selected bar so to do
that we just need to change our bar
index to Bar time however we also need
to inform or tell the label function
that we are working with bar time and
not a bar index so by default the label
function uh the x value the first value
in this label function is a bar index so
the very first bar on our chart will be
bar index zero and then the latest bar
on our chart will be however many bars
are drawing on our chart in this case we
don't want to use bar indexes or indices
we want to use bar time so to do that I
need to tell my label function that the
x loock value is supposed to be xlock
bar time instead of bar index so we're
overwriting the default value for xlock
from bar index to Bar time we're getting
the bar time as a user input the user
must select the bar with their Mouse and
then if we're on the final bar on our
chart and the user has selected a bar
time then we'll draw a new label on that
bar can save my code here now nothing's
going to change because we've already
added the script to our chart so when I
come up to the settings menu and go to
input uh the select bar input is going
to be set to the default value which is
1970 1st of January 1970 which is when
the Unix Tim stamp begins calculating
from but again that's not information
you need to know about what you do need
to know is that if you want to be able
to just select a bar without coming in
here and setting your year and date and
time and all of that which is annoying
and clunky what we want to do is remove
our script from our chart and then add
it back onto the chart and now you'll
see this pop up
select the select bar time for this
script so my script is named after my
website but here would be your script
title and now you'll see that my script
has a vertical line and whichever bar I
click on will be the bar that we draw
our label on so you can hold control or
command on a Mac to tell pinescript
where you want to zoom in so if I hold
down control and I go all the way back
let's do a bar in here let's do this uh
this top bar here when I click on this
bar like so we are getting a label
drawing now the label is all the way
down here I'm not exactly sure why
that's happening it should be drawing on
the bars high so maybe I need to specify
my y loock value here y loock do above
bar let's try that save my code there we
go that's better so now the label is
drawing above the bar that I selected
which was this swing High bar here and
we're getting our for Loop data drawing
into a label over the past 10 bars
starting from this bar and we can do our
debugging across those bars to make sure
and confirm that all of these values
here are accurate I should mention that
you can also debug custom functions as
well in order to do that uh this is a
custom function defined the very last
line in your function is what the
function returns and so if you wanted to
debug um what your custom function is
doing you could do something like this
test two and test one so test one is
going to be a local variable created
within our custom function and it's
going to be set to this value that's
inputed into our custom function * 2.5
and then test two is going to be this
same value Time 4 and now if I create a
new value here called custom fun is set
to FN um let's set it to one that way we
can very easily see that this value is
2.5 and this value is four and now if I
plot
Char our custom fun function value and I
give it a title let's just title it
custom function number one and I save my
code and open the data window you'll
notice that this number here is four so
what's happening is our custom function
is doing whatever it does here executing
this code and then the function outputs
the final line of code here so whatever
this final line of code is is the
function's output so in this case that's
test * 4 so what if we wanted to um
multiply Test 2 by test one uh so test
one multiplied by four let me save my
code now keep an eye on this number that
should be 2.5 * 4 which gives us 10 but
what if we wanted to know what test one
was inside of our function this is where
things get a bit complicated those of
you in the Mastery course will probably
be more familiar with custom functions
as we cover a whole module in there on
this subject as well as what I'm about
to show you which is tups so if your
head is spinning right now don't worry
that's normal this stuff is bit
complicated takes a while to wrap your
head around uh but basically what we
need to do with our custom function is
return two values to do that we use the
square brackets and I can put test one
and test two in here and now this line
of code will not compile because we're
returning a tple this function is
returning two values now so what we
would need to do here is open some
square
brackets and and we need to specify the
two values from our function and now I
actually need to get rid of this data
type because pinescript will
automatically detect what these two
values should be and so our function is
now outputting two values test one and
test two and if I want to plot the first
value that'll be this value here so
custom fun one and if I paste this down
here and change this to two and that to
two save my code we'll now be getting
two values down here here the first one
is test one which is going to be this
value *
2.5 and the second value here is going
to be test two which is test 1
multiplied by 4 which gives us 10 so
hopefully that makes sense if it doesn't
just re-watch this last part of the
video a few times and eventually it will
click so that'll do for today's video
I'll leave the source code to this below
um a link to the source code below for
those of you who want to dive into the
code and actually play around with it
yourself I know this lesson wasn't as
exciting as some of our other lessons
creating strategies and indicators and
tools but this is an important subject
that I get asked about pretty often and
it's something we all need to be aware
of as Pine scripts there will come times
when your script is not doing what you
want it to do and depending on the
complexity of your script that can be a
little difficult to pin down what's
going wrong these are a few methods you
can use to figure that out with all that
said I'll leave this video here thanks
for watching as always make sure to
subscribe if you haven't already cuz
I'll be back real soon with a new
pinescript video if you want to level up
your PIN scripting make sure to check
out our courses at pinescript
mastery.com there's a free basic course
there with several hours of content for
those of you who are new to pinescript
if this lesson went way over your head
then you might want to start there but
anyway thanks for watching I love you
guys best of luck with your trading and
I'll speak with you soon take care