# Plot! inside a function
**URL:** https://discourse.julialang.org/t/plot-inside-a-function/93597
**Category:** New to Julia
**Tags:** plotting, plots
**Created:** [January 26, 2023, 10:21pm UTC](https://discourse.julialang.org/t/plot-inside-a-function/93597 "2023-01-26T22:21:22Z")
**Posts on this page:** 7
**Page:** 1
### Author:  [@jimmmm](https://discourse.julialang.org/u/jimmmm)
#### Post date: [January 26, 2023, 10:21pm UTC](https://discourse.julialang.org/t/plot-inside-a-function/93597/1 "2023-01-26T22:21:22Z")
So, to keep things on a plot (like Matlab’s “hold on”), you call plot as plot!(…).
If I make a function such as
function plotsomething(input)
intermediate result = do something with input
plot(intermediate result)
end
Is there an easy way to call plotsomething!() instead of plotsomething() and have it apply the “hold on” properties to the plot I used in the function?
---
### Author:  [@liamfdoherty](https://discourse.julialang.org/u/liamfdoherty)
#### Post date: [January 26, 2023, 11:38pm UTC](https://discourse.julialang.org/t/plot-inside-a-function/93597/2 "2023-01-26T23:38:01Z")
There are two things I can think of, maybe one of them can fit your needs. The first is to write some separate function `f(input) = # do something with input`, and then you can have
```julia
function plotsomething(input)
intermediate_result = f(input)
plot(intermediate_result)
end
```
and
```julia
function plotsomething!(input)
intermediate_result = f(input)
plot!(intermediate_result)
end
```
(the definition of `f` is just to save on lines of code). The other possibility is something like
```julia
function plotsomething(input, hold_on = true)
intermediate_result = f(input)
if hold_on
plot!(intermediate_result)
else
plot(intermediate_result)
end
```
You can also elect to make an empty plot with `plt = plot()` ahead of time and pass it into the function `plotsomething`, and then add what you want from the function with `plot(plt, ...)` where the ellipses indicate what you would put in `plot!` if you were simply adding to the last edited plot.
Hope something here helps!
---
### Author:  [@rafael.guerra](https://discourse.julialang.org/u/rafael.guerra)
#### Post date: [January 27, 2023, 12:52am UTC](https://discourse.julialang.org/t/plot-inside-a-function/93597/3 "2023-01-27T00:52:07Z")
In addition to the above comments, another thing that can help is to add variable arguments:
```julia
using Plots
function plotsomething!(p, input; args...)
y = input .^ 2
plot!(p, input, y; args...)
end
p = plot()
plotsomething!(p, -5:5)
plotsomething!(p, -7:2; ls=:dash)
plotsomething!(p, [-2,2]; ms=8, st=:scatter)
```
---
### Author:  [@BeastyBlacksmith](https://discourse.julialang.org/u/BeastyBlacksmith)
#### Post date: [January 27, 2023, 7:59am UTC](https://discourse.julialang.org/t/plot-inside-a-function/93597/4 "2023-01-27T07:59:51Z")
You could also use a callback:
```julia
using Plots
function plotsomething(input; pf = Plots.plot, args...)
y = input .^ 2
pf(input, y; args...)
end
plotsomething(-5:5)
plotsomething( -7:2; pf = plot!, ls=:dash)
```
---
### Author:  [@rafael.guerra](https://discourse.julialang.org/u/rafael.guerra)
#### Post date: [January 27, 2023, 8:41am UTC](https://discourse.julialang.org/t/plot-inside-a-function/93597/5 "2023-01-27T08:41:20Z")
Hi Simon, does the callback solution allow handling independently different plot objects p1, p2, … ?
I get the following error:
```julia
p2 = plotsomething([-10,2]; ms=8, st=:scatter)
plotsomething([2,2]; pf=p2, ms=8, st=:scatter)
ERROR: MethodError: objects of type Plots.Plot{Plots.GRBackend} are not callable
```
---
### Author:  [@BeastyBlacksmith](https://discourse.julialang.org/u/BeastyBlacksmith)
#### Post date: [January 27, 2023, 8:55am UTC](https://discourse.julialang.org/t/plot-inside-a-function/93597/6 "2023-01-27T08:55:09Z")
You could do it loke this:
```julia
using Plots
function plotsomething(input, p = nothing; pf = Plots.plot, kwargs...)
y = input .^ 2
if p === nothing
pf(input, y; kwargs...)
else
pf(p, input, y; kwargs...)
end
end
p1 = plotsomething(-5:5)
p2 = plotsomething(-7:7)
plotsomething( -7:2, p1; pf = plot!, ls=:dash)
```
Or create a one and a two argument method.
---
### Author:  [@jimmmm](https://discourse.julialang.org/u/jimmmm)
#### Post date: [January 27, 2023, 11:28am UTC](https://discourse.julialang.org/t/plot-inside-a-function/93597/7 "2023-01-27T11:28:14Z")
Thank you everyone for the responses. They really helped get a sense of what all of the options are.