Beginner Guide to ARRAYS in PINE SCRIPT

hey traders let's jump into the world of
arrays in behind script so first of all
what is an array an array can be thought
of as a collection of data types
so arrays can be used to store multiple
values in one data structure or
collection of data
think of them as a better way to handle
cases where you would otherwise need a
set of variables named for example price
0 price 1 price 2 and so on except that
our list of variables in an array can be
dynamically increased or decreased in
size so rather than having hard-coded
variables for each value you can have a
list of values assigned to one array
variable and those values can change
over time
the number of values saved can change
over time and they're just a more
efficient way of handling cases where
you need multiple forms of data saved
under one collection now arrays are an
advanced feature used for scripts
requiring intricate data handling so if
you are a beginner pine programmer you
should become more familiar with other
more accessible pine features before you
tackle arrays that is why i've put this
lesson towards the end of this course
they are not for the faint-hearted in
terms of inexperienced programmers
now pine arrays are one-dimensional
which means they look something like
this we have our array and then our
array has a list of values and these are
our values here
and it's one dimensional it that's it
you can't have uh values within values
and like stack values like this
that's not possible in arrays we just
have one list of data
and those values belong to our overall
array
and we reference the values using what
is called an index so an index starts at
zero and extends to the number of
elements in the array minus one so if we
have one two three four five elements in
our array here x in this case would be
array index zero
and the final
array index would be 4 but because we
start counting from 0 that means we have
5 different
values stored in our array now all
elements of an array are of the same
data type which can be integer whole
numbers floating point decimal numbers
boolean values color string line label
box or tables and they are always of
series form which means they can have
different values across different bars
on our chart arrays are referenced using
an array id similar to line or label ids
so for example we create an array here
called a
and this is set to
some code that creates an array when we
want to reference that array we need to
use the array
dot control space will give us a list of
functions that we can use to reference
our array and manipulate that array and
we need to pass in our array id which is
the name of the array variable we'll get
to this in a moment in the pine editor
and this will make more sense but if
you're familiar with arrays in other
languages for example java
if you've ever used java
an array in java looks something like
this you have your array id or variable
name and then you open square brackets
and you reference your id within those
square brackets and that gives you the
array pretty much identically to how we
reference close open high close and
indicator values using the historical
operator in pan script other languages
typically use that
syntax for dealing with arrays but in
pinescript things are a little bit
different we use this square bracket
syntax for referencing series values so
open high low close volume indicator
values etc over historical data and the
number we put in here corresponds to the
bar index on our chart that is how
arrays normally work in other languages
except that in panscript you cannot
change the value of a series so you
can't
change the value of the closing price
from 10 bars ago
by
reassigning it to a different value
this is impossible in pine so instead if
you want to do something like this if
you want to deal with a collection of
data and you want to manipulate that
data we need to use arrays to achieve
that and they behave a little bit
differently we use the get and set
functions for example to read and write
values
of array elements and array values can
be used in all pine expressions and
functions where a value of series form
is allowed so a series form can just be
thought of as open high low close values
volume everything i just said indicator
values wherever you can use them in your
script you can use array values as well
now arrays in pine can be sized
dynamically so that means the number of
elements in the array can be modified
on each bar on our script and it can
vary across bars and multiple arrays can
be used in the same script
and the maximum size of arrays so the
maximum amount of values you can store
in an array is 100 000 values which is a
lot of values i don't think there will
be many times if ever that you would run
into that
limitation so let's explore how we
declare arrays
so this is the syntax for declaring an
array we need to specify the type
and then we use the square brackets to
indicate that this variable is not a
normal variable it's an array type
then we have our identifier which is our
variable name the name of the array or
the array id
and then we have our expression which
creates the array so let's jump into the
editor really quickly and i'll show you
an example of this so for example let's
say we want to create an array that
holds price values or indicator values
anything with a floating point number a
decimal number in it the way we do that
is there are several ways we can do this
but let me show you one way the first
way we can do this is we can write out
the data type that we want to work with
so in this case that would be float
then we need to put two square brackets
at the end to signify that we want to
create a float array
and then we need to specify a name for
this array
so for this we'll just call it price
array
and then we need to initialize this as
something
um so to create a new array there are a
couple of ways we can do this the first
way is to just type out array the array
name space so array dot control space or
command space
and there are two different types of
functions we can create here that we can
use here to create an array we can use
from
so notice these data types down here we
can create an integer float bool string
label line etc using the from function
and then these arguments you see here
arg0 arg1 dot dot dot
we can specify the array values that we
want in our array using this from
function this will create an array from
the values we put in there there's also
the new function so array dot new
underscore and then the data type so we
could create a new float array and we
can specify the size of the array and
the initial value of every
element within that array but before we
get to this which is a little bit more
complicated let's just show you guys how
to use the from so if i write out from
here and we could say
let's specify our values as 0.1
2.5 and let's go 5.0 now when i save
this code this should compile without
any problems there we go and now let's
create a label that displays how many
values are in our array to do that i'm
going to create an if statement here and
i'm going to say if bar state dot is
last so if this is the last bar in our
chart
then create a new label at the current
bar index and place
place it at value 0 and the text will
say
array size
is
str.2 string remember we need to convert
numbers to strings before we can add
them to a string so tostring
array dot control space
size and then we need to pass in the id
of our array which is price array the
name of the variable so here i can say
price array
close those two
parentheses off and the third one
and now when i save my script we should
be getting
three drawing onto the chart there we go
because we have one two three elements
in our array if we want to display um
the first value in our array
then we need to use the str.2 string
function again and then we need to use
the array.get
function to get the value we want from
our array so now for the array.get
function we need to pass in the array we
want to reference which is our price
array again
and then the element index that we want
to retrieve or get from our array so
remember everything in programming
starts from 0. so if we put zero in here
we will be getting
0.1 drawing
as our first value here so if i save my
script bring this down a little first
value
0.1 if we want to get the last value
then we would need to pass in 0
1 2 so i'll put 2 in here that will
reference the third value remember
counting from 0 0 1 2
save my code we'll get 5.0 or just five
drawing on there and i accidentally took
out my new line
escape character there we go
so last value in our array is five
so this is the basic core fundamentals
of arrays
we create an array we can get the size
of our array here which is useful for
things like iterating through the array
it's called iteration when we loop
through the values of an array which
i'll show you how to do in a future
lesson i don't think we'll cover that in
this lesson we'll keep it as simple as
possible this is just an introduction to
arrays so for now let's just keep it
simple we've created a very basic array
here we're getting the size of the array
and we're referencing values from the
array let's say we want to change a
value in the array to do that let's do
it on the very last bar here as well to
change an array value we can say array
dot control space and we can use the set
function so i can say set price array
and then we need to specify the index
of the value so we're drawing the last
value in our array here let's just
reference that so if i put two in there
we're now saying
set the
third
value in our array to whatever we put in
here next so if i put
um 33 in here when i save my script i
believe we'll get an error here because
33 is not a floating point number
there's no decimal here this is an
integer so if i save my code i believe
we'll get an error oh no pine script
converted that into a float that's good
so now if we tried to create this as an
int array and we passed in floating
points we'll definitely get an error
here
because uh declared type array is not
compatible with the assigned type
so these types are floats
and we created an integer array so
floats are not compatible with integers
but apparently integers are compatible
with floats which is good so if i change
this back to float pinescript is
converting this whole number into 33.0
so now let's save the code our last
value here is 33 because we are
overriding our last value by setting the
value index of 2
on this price array to 33 and then when
we draw that to the chart here and we
get that same
index value from our array
it's changed to 33. so that's how you
create an array with predefined values
this is how you change a value in your
array
and this is how you draw
uh the value to the chart using a label
so let's look at some other examples
here let me just quickly show you what
happens when we use the new underscore
float array function so this will now
create a new array with the specified
size and the specified initial value so
let's create an array with the size of 1
for example and the initial value of 0.0
when i save my code we should be getting
another error here because of the code
down here is referencing
the number 2 index which is
the third value in our array and we just
created an array with only one value in
it so if i save my code yeah we're
getting an error up here and it should
say array index out of bounds there we
go index two is out of bounds array size
is one so now if i change my array size
to two we'll still get an error because
remember the size of our array
counts from one so if we put one in here
that means we have one value if we put
two that means we have 2 but our index
starts from 0. so if we put 2 in here
we're actually referencing the
third value in our array so if i save my
code we should still get this error we
do
if we change our size to three
now we have the same array size that we
started with before when we created our
array using the from function so we have
three possible values in our array so
now when i save the script we should be
getting 33 drawing back onto our chart
because of our set function is
overriding the third value so let me
save my script there we go we have 33
drawing as our last value if i remove
this
array.set code and save my code now the
last value is zero because
of this
when we use the array.new function for
any of our data types
the initial value is
assigned to every element in our array
so if i change this to 2.5 for example
save my code this will now say 2.5 is
the last value and every value in our
array is 2.5 by default until we
override that so now it's important to
mention that arrays behave identically
to other variables in terms of how the
pine script engine handles them
what i mean by that is when we create
this variable this array variable
it is recreated on every single bar on
our chart the same way any other
indicator value would be so what i mean
by that is
if i create a new variable here called
my variable and i set it to 0 and we
plot my variable and then when i save my
code we should be getting 0 drawing on
every single bar on our chart
and if i were to increment my variable
by one on every bar on my chart this
will now plot one on every bar so when i
save my code now every bar says one
that's because this my variable is
recreated on every new bar that gets
loaded onto our chart if i turn this
into a var variable however and i save
my code now we'll be plotting how many
bars were plotted onto our chart because
myvariable gets incremented on every
historical bar that our script runs on
and because we use the var keyword
this
variable value does not get reset on
every new bar
and it persists
across all of our price action
we can use the same technique with our
arrays so for example let's do the same
thing with our array let's count how
many bars are on our chart
to do that we'll get rid of this code
and get rid of this commented code and
let's create a new array called var
count array is set to array
dot new underscore float and we'll give
it an initial size of zero let me copy
this into our
array variables here and we'll come back
to this in a moment
but for now i'll set this to the first
value in our array
now the way we add a value to an
existing array is using the push
function so array dot push
will append or add whatever value we put
into this function to the given array so
if i put in count array here
and then let's just push the current
closing price of every bar on our chart
to this array so now when i save my code
we should be getting an array size of
yeah
4149 which is how many bars on our chart
and you can see the first value here
0.04951
i'm sure we'd all love to have uh bought
bitcoin back when it was worth uh 5
cents
let's go back and check that out make
sure that's an accurate number and
indeed it is back in july of 2010
bitcoin was worth five cents uh how
things have changed since then eh and we
have our array size of 4149.
um let's get rid of our first value here
and say
bar count
and then we'll add
str.2 string the bar index value
to our label save our code and now you
can see that our bar count is
4148 that's because our bar count begins
counting from zero
so this is technically 4149
but our array size counts our zero index
is one so this is where it gets a little
bit confusing when you are referencing
your array values it starts from zero
but your array size includes the element
at array zero as one so if you've got an
array
with three values in it
the array size is three but to reference
the third value you need to put in the
index of two so i know it gets quite
confusing don't worry with practice
you'll get the hang of this so let me
change this back to zero and let's say
we want to reference the last
bar
value so if i change this to last
value in our array and we use the
array.get function we pass in our count
array
and then
we now want to reference the final value
in our array
the way we can do that is using the
array size counter
function
and then subtracting 1 from that
so if i cut this out and we'll just
create a new variable here called size
paste that in so now we're creating a
new variable called size which is
assigned to array.size and then we pass
in our array id
this size value will now be four one
four nine
so if we want to reference the last
value in our array using the array.get
function we need to pass in size
minus one and i'll show you why we need
to subtract one from our size if i get
rid of that and i save my script we'll
get an error array index out of bounds
because 4149 is exactly the same
index as our array size but remember our
array values start from zero so we need
to subtract one from this to get the
final
value
in our array so now when i save the code
we should be getting the current closing
price so save and there it is
five zero three one nine and it's
changing as price action changes so i
think that will do it for the
introduction to arrays in future lessons
we'll build on this information and try
different
techniques for dealing with arrays to be
perfectly honest with you i personally
have never used arrays in my scripts
i've never really encountered a
situation where i needed to it's a
feature in pine script that due to the
nature of pine script isn't as commonly
used as it would be in other programming
languages but nonetheless we'll explore
this further in the lessons to come so
i'll see you there
i hope you found this lesson interesting
if you did and you want to learn more
about arrays make sure to check out my
pinescript mastery course at
pinescriptmastery.com the course
explores arrays in a lot more detail
including some practical example scripts
and the course obviously also covers
many other things relating to advanced
and complex features of pinescript so if
you're interested in that make sure to
come and check this out and if you're
not interested in the mastery course but
you still want to learn more pinescript
at least make sure to hit the subscribe
button because i will be back very soon
with more lessons good luck with your
trading good luck with your coding and
i'll speak with you soon
you