# Plots.jl: Assigning seriescolor using ColorGradient for line plot
**URL:** https://discourse.julialang.org/t/plots-jl-assigning-seriescolor-using-colorgradient-for-line-plot/17099
**Category:** Visualization
**Tags:** question, plotting
**Created:** [November 2, 2018, 7:49pm UTC](https://discourse.julialang.org/t/plots-jl-assigning-seriescolor-using-colorgradient-for-line-plot/17099 "2018-11-02T19:49:53Z")
**Posts on this page:** 15
**Page:** 1
### Author:  [@Micah\_BL](https://discourse.julialang.org/u/Micah_BL)
#### Post date: [November 2, 2018, 7:49pm UTC](https://discourse.julialang.org/t/plots-jl-assigning-seriescolor-using-colorgradient-for-line-plot/17099/1 "2018-11-02T19:49:53Z")
I am having trouble using a ColorGradient to set the color levels of a dynamic number of series.
I can get the colorgradient to work if I use heatmap:
```julia
A = [i for i=1:100, j=1:100]
heatmap(A, c=ColorGradient(:inferno))
```
But for line plots it assigns the same color to all series:
```julia
N=40
n = 10; x = range(0,step=1,length=n); y=rand(n,N);
plot(x,y,c=ColorGradient(:inferno))
```
I am using Julia 1.0.1, Plots v0.21.0 and the GR v0.35.0 backend.
Any help would be appreciated.
Thanks!!
---
### Author:  [@BLI](https://discourse.julialang.org/u/BLI)
#### Post date: [November 2, 2018, 9:14pm UTC](https://discourse.julialang.org/t/plots-jl-assigning-seriescolor-using-colorgradient-for-line-plot/17099/2 "2018-11-02T21:14:50Z")
It is not quite clear to me what you want to do. Do you want to:
1. Plot, say, 3 curves, with different color, e.g., one red, one blue, and one green?, or
2. Do you want to plot one curve which changes color from, say, red to blue, along the curve?
Case 1.a: Julia v. 0.6.x allowed to make a vector of colors using the `linspace()` function, something along `linspace(colorant"red",colorant"blue",5)` would make a vector of 5 colors in the range from color `colorant"red"` and color `colorant"blue"`.
Unfortunately, function `linspace()` has been removed, and the replacement, `range()` doesn’t support color argument. This is really unfortunate!
Anyway, the `Plots` syntax is that colors should be a row matrix, so colors in a vector need to be converted to colors in a row matrix.
You can, of course, still make the row matrix of colors manually:
```nohighlight
plot([sin,cos,atanh], lc=[:red :blue])
```
Here, the list of functions will cycle through the row matrix of line colors.
Case 1.b: colors from color gradient.
Use a built-in color gradient, or design your own. Say you want to make your own, `my_cgrad`…
```nohighlight
my_cgrad = cgrad([:red, :yellow, :blue])
```
makes a color gradient that starts in red, goes through yellow and ends up in blue. You need a minimum of two color elements in the argument vector.
To pick plot colors from the color gradient, do the following:
```nohighlight
plot([sin, cos, atanh], palette = my_cgrad)
```
Case 2: Suppose you instead want to change the color along the line – perhaps mainly useful in parametric plots. This can be done as follows:
```nohighlight
x = range(0,stop=2pi,length=50)
plot(sin.(x),cos.(x),lc=my_cgrad,line_z=x)
```
---
### Author:  [@Micah\_BL](https://discourse.julialang.org/u/Micah_BL)
#### Post date: [November 2, 2018, 9:32pm UTC](https://discourse.julialang.org/t/plots-jl-assigning-seriescolor-using-colorgradient-for-line-plot/17099/3 "2018-11-02T21:32:02Z")
Thanks for the reply!
I am looking to do more along the lines of case 1. Basically I have a mxn Array which represents n different curves I would like to plot. I want to use a color gradient to choose the color for those n different curves but order it based on the column index of the Array. So if I am using the `:blues` ColorGradient, for example. I want the first curve (first column in the array) to be the darkest color available in the gradient, the last curve to be the lightest, and automatically select the appropriate colors in between in the gradient.
The palette method gets me close but when I do something like this:
```julia
N=40
n = 10; x = range(0,step=1,length=n); y=rand(n,N);
plot(x,y,palette=:blues)
```
It selects the colors from the gradient seemly randomly.
---
### Author:  [@BLI](https://discourse.julialang.org/u/BLI)
#### Post date: [November 2, 2018, 9:58pm UTC](https://discourse.julialang.org/t/plots-jl-assigning-seriescolor-using-colorgradient-for-line-plot/17099/4 "2018-11-02T21:58:05Z")
Does this mean that you _really_ would like to use a row matrix of colors? In the “good old days” of `linspace`, one could do, say,
```nohighlight
CLIST = reshape(linspace(colorant"blue",colorant"red",n),1,n)
plot(X,lc=CLIST)
```
Here, `CLIST` is a vector of `n` colors reshaped into a row matrix. Assumin that matrix `X` has `n` columns, the color of the first column equals the color of the first element in `CLIST`, the color of the second column of `X` equals the second element in row matrix `CLIST`, etc.
Another option: I think it is possible to specify that you want, say, `n` colors, and that you want these to be picked from some list of colors in such a way that they are the `n` that are easiest to distinguish. Don’t recall the syntax for doing this, though.
---
### Author:  [@Micah\_BL](https://discourse.julialang.org/u/Micah_BL)
#### Post date: [November 2, 2018, 10:04pm UTC](https://discourse.julialang.org/t/plots-jl-assigning-seriescolor-using-colorgradient-for-line-plot/17099/5 "2018-11-02T22:04:55Z")
yes, i was assuming there was an internal method to Plots to select the colors when passing `seriescolor=ColorGradient(:blues)`. But alternatively, it sounds like I am looking for a way to create a row vector of `n` colors that are along a gradient or between two defined colors. Any way to do this in 1.0 without `linspace`?
For context: I am trying to show how a `m` length variable changes over a number of iterations so would like a gradient to show this rather than distinct colors since there can be \>100 difference curves.
---
### Author:  [@BLI](https://discourse.julialang.org/u/BLI)
#### Post date: [November 2, 2018, 10:11pm UTC](https://discourse.julialang.org/t/plots-jl-assigning-seriescolor-using-colorgradient-for-line-plot/17099/6 "2018-11-02T22:11:38Z")
Ah… `range` _does_ work with colors! I tested it in a REPL where I had not used `using Plots`…
So – this works, I think…
```nohighlight
using Plots;
n=20;
X=rand(100,n)
CList = reshape( range(colorant"red", stop=colorant"blue",length=n), 1, n );
plot(X,linecolor=CList)
```
See [Introduction · Colors](http://juliagraphics.github.io/Colors.jl/latest/) for some more.
---
### Author:  [@Micah\_BL](https://discourse.julialang.org/u/Micah_BL)
#### Post date: [November 2, 2018, 10:18pm UTC](https://discourse.julialang.org/t/plots-jl-assigning-seriescolor-using-colorgradient-for-line-plot/17099/7 "2018-11-02T22:18:43Z")
Cool that works thanks!
Not sure if this is already available but it would be neat if there was a way to specify how the colors are picked from a palette. So I could do what I wanted with something like
```julia
plot(X,palette=my_cgrad, colorIndex=Col.index)
```
---
### Author:  [@BLI](https://discourse.julialang.org/u/BLI)
#### Post date: [November 3, 2018, 7:49pm UTC](https://discourse.julialang.org/t/plots-jl-assigning-seriescolor-using-colorgradient-for-line-plot/17099/8 "2018-11-03T19:49:45Z")
Would probably be nice. I’m not a developer in any way, just a simple early user :-). Others may have to look into that.
---
### Author:  [@mkborregaard](https://discourse.julialang.org/u/mkborregaard)
#### Post date: [November 4, 2018, 10:01am UTC](https://discourse.julialang.org/t/plots-jl-assigning-seriescolor-using-colorgradient-for-line-plot/17099/9 "2018-11-04T10:01:24Z")
Eh, `plot(X, palette = :inferno)` is already valid Plots syntax?
Note that Plots cannot know how many series you will add in the future, so when specifying a palette it will always try to select each color to be as widely spaced on the color gradient as possible.
If you know you have 5 series and want them spaced on the color gradient sequentially, you can use `color` and spread `line_z` over the 5 series:
`plot(rand(20,5), color = :RdYlBu, line_z = (1:5)')`
You can also just supply a vector with the color of each line to `palette`.
---
### Author:  [@Micah\_BL](https://discourse.julialang.org/u/Micah_BL)
#### Post date: [November 5, 2018, 1:05am UTC](https://discourse.julialang.org/t/plots-jl-assigning-seriescolor-using-colorgradient-for-line-plot/17099/10 "2018-11-05T01:05:14Z")
Thanks! That works well if I use the GR backend. However with pyplots I get an error:
```julia
Error showing value of type Plots.Plot{Plots.PyPlotBackend}:
ERROR: MethodError: no method matching py_color(::ColorGradient, ::Nothing)
Closest candidates are:
py_color(::ColorGradient) at C:\Users\micah\.julia\packages\Plots\rmogG\src\backends\pyplot.jl:59
py_color(::Colorant, ::Any) at C:\Users\micah\.julia\packages\Plots\rmogG\src\backends\pyplot.jl:60
py_color(::Any) at C:\Users\micah\.julia\packages\Plots\rmogG\src\backends\pyplot.jl:56
```
Any ideas?
---
### Author:  [@mkborregaard](https://discourse.julialang.org/u/mkborregaard)
#### Post date: [November 5, 2018, 10:07am UTC](https://discourse.julialang.org/t/plots-jl-assigning-seriescolor-using-colorgradient-for-line-plot/17099/11 "2018-11-05T10:07:07Z")
Bug ☹
---
### Author:  [@axsk](https://discourse.julialang.org/u/axsk)
#### Post date: [December 4, 2019, 3:01pm UTC](https://discourse.julialang.org/t/plots-jl-assigning-seriescolor-using-colorgradient-for-line-plot/17099/12 "2019-12-04T15:01:57Z")
I share the same desire as @Micah_BL (over and over, and never found a solution I could stick with).
While I would like `plot(X, palette = :inferno)` to work out of the box, it doesn’t lead to the desired result, as you explained above.
> Note that Plots cannot know how many series you will add in the future
Wouldn’t just spreading the colors out evenly among the current given series be a sane default?
Also `plot(rand(20,5), color = :RdYlBu, line_z = (1:5)')` does not seem to work anymore. It gives me 5 lines of the same color ☹
---
### Author:  [@mkborregaard](https://discourse.julialang.org/u/mkborregaard)
#### Post date: [December 4, 2019, 6:13pm UTC](https://discourse.julialang.org/t/plots-jl-assigning-seriescolor-using-colorgradient-for-line-plot/17099/13 "2019-12-04T18:13:53Z")
Wow, what happened there?
---
### Author:  [@mkborregaard](https://discourse.julialang.org/u/mkborregaard)
#### Post date: [December 5, 2019, 11:57am UTC](https://discourse.julialang.org/t/plots-jl-assigning-seriescolor-using-colorgradient-for-line-plot/17099/14 "2019-12-05T11:57:37Z")
The last issue will be fixed in [https://github.com/JuliaPlots/Plots.jl/pull/2305](https://github.com/JuliaPlots/Plots.jl/pull/2305)
---
### Author:  [@mkborregaard](https://discourse.julialang.org/u/mkborregaard)
#### Post date: [December 5, 2019, 11:58am UTC](https://discourse.julialang.org/t/plots-jl-assigning-seriescolor-using-colorgradient-for-line-plot/17099/15 "2019-12-05T11:58:40Z")
> [@axsk](#):
>
> Wouldn’t just spreading the colors out evenly among the current given series be a sane default?
And disable the functionality of assigning a new color when adding a series? No, not in my opinion.