Color coded plot Python

Question

I have a color coded plot. Here is a part of the code:

fig = plt.figure(figsize=(10,10))
color_scheme = plt.get_cmap('cool')
gs = gridspec.GridSpec(1, 1)
ax1 = plt.subplot(gs[0])
gs.update(left=0.15,bottom=0.15,right=0.80,top=0.95)
cax = fig.add_axes([0.80, 0.15, 0.03, 0.80])

im = ax1.scatter(x, y, c=z, edgecolors='black', marker='.', s=40, lw=1, cmap=color_scheme, vmin=0, vmax=10)
cb = fig.colorbar(im, cax=cax)
for t in cb.ax.get_yticklabels(): t.set_fontsize(12)

The problem is that I want to connect the dots with a line, and it doesn't work to use marker='-' and it also doesn't work if I use ax1.plt. How can I do this?
What I actually need is to fit a line to some points and color it the same color as the points (the points I fit to will all have same color)

heltonbiker · Accepted Answer · 2016-08-05 15:04:26Z

2

Instead of using

ax1.scatter(x, y, ...)

use

ax1.plot(x, y, 'o-', ...) # three dots meaning you can configure markers, linestyle, etc.

This works bacause of 'o-' argument, which is a line plot with markers at every data point.

answered Aug 5, 2016 at 15:04

heltonbiker

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3 Comments

pathoren Over a year ago

Does this really work? I am not sure if the standard plot can handle colormaps.

Silviu Over a year ago

As I say plt.plot doesn't handle colormaps

heltonbiker Over a year ago

You are right about the colormaps. But how you expect the lines connecting the dots to be colored? If you want a single-colored line, you could plot it using plot and then overlay the colormapped markers using a subsequent call to scatter. Now if you want each line segment to be colored, then you would have to plot each segment independently, or use matplotlib shapes for that (not fast).

pathoren · Accepted Answer · 2016-08-05 15:06:22Z

1

Plot the same x and y-data separately with a standard ax.plot behind your scatter plot.

ax1.plot(x, y, '-')
im = ax1.scatter(x, y, c=z, edgecolors='black', marker='.', s=40, lw=1, cmap=color_scheme, vmin=0, vmax=10)

This should give you your cmapped scatter plot with the lines behind the scatter-points.

answered Aug 5, 2016 at 15:06

pathoren

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3 Comments

Silviu Over a year ago

But if I do that, will the line has the same color distribution as the plot? I think it will be just blue

pathoren Over a year ago

The default is ofcourse blue, and as you point out plot does not handle cmaps afaik. However I thought the main goal was to just connect the points?

Silviu Over a year ago

What I actually need is to fit a line to some points and color it the same color as the points (the points I fit to will all have same color).

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