Shade area between 2 y coordinates in matplotlib

Question

I'm trying to create a shaded rectangle based on two vertical coordinates (the length of the rectangle should span the whole x axis). I've tried to use fill_between with the following (p1 & p2 are the data coordinates):

f, ax1 = plt.subplots()   
x = np.linspace(200,300,2000)
y = x**(2)
y1 = x
p1 = 4700
p2 = 7700

ax1.plot(x, y, lw=2)
ax1.set_xlabel('Temperature $[K]$', fontweight='bold')
ax1.set_ylabel('Pressure $[mb]$', fontweight='bold')
ax1.fill_between(x, y1.fill(p1), y1.fill(p2))

But i'm getting the following error:

TypeError: ufunc 'isfinite' not supported for the input types, and the inputs could not be safely coerced to any supported types according to the casting rule ''safe''

What is wrong? Any better way to do this?

Thank you!!

`y1.fill(p1)` doesn't return an array! – Jacques Gaudin Jun 01 '18 at 15:39 — Jacques Gaudin, Jun 01 '18 at 15:39

ImportanceOfBeingErnest · Accepted Answer · 2018-06-01T15:47:10.147

3

Possibly you mean to use axhspan.

p1 = 4700
p2 = 7700
ax1.axhspan(p1, p2, color="limegreen", alpha=0.5)

edited Jun 01 '18 at 15:47

answered Jun 01 '18 at 15:25

ImportanceOfBeingErnest

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Thanks! but can I make the shaded region more transparent and in another color? – ValientProcess Jun 01 '18 at 15:44

sacuL · Answer 2 · 2018-06-01T16:02:38.907

1

IIUC, the issue is with the use of the .fill() function. You can avoid that, using fill_between with your x array and just the p1 and p2 values, as fill_between can accept scalar values for y1 and y2.

ax1.fill_between(x, p1, p2)

Note, you can change the color and transparancy easily by adding a color and alpha argument:

ax1.fill_between(x, p1, p2, color='limegreen', alpha=0.5)

edited Jun 01 '18 at 16:02

answered Jun 01 '18 at 15:27

sacuL

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Jacques Gaudin · Answer 3 · 2018-06-01T15:47:38.073

0

The fill method of an array doesn't return an array, it returns None.

edited Jun 01 '18 at 15:47

answered Jun 01 '18 at 15:42

Jacques Gaudin

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score -2 · Answer 4 · answered Jun 01 '18 at 15:28

-2

You've misunderstood fill_between. When you use it is advisable to express y as a function:

def y(x):
    return x**2
section = np.arange(start,end,0.1)
plt.fill_between(section,y(section))

will do the job with suitable values for start and end.

answered Jun 01 '18 at 15:28

Paula Thomas

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The way `fill_between` is used in the OP is correct, but `y1.fill(p1)` is `None`, not an array. – Jacques Gaudin Jun 01 '18 at 15:43
Wrong. I have used it precisely this way - it works. – Paula Thomas Jun 01 '18 at 15:47
This answer is correct in itself, but does not do what the question asks for because it fills the resgion between y=0 and the line defined by y=x**2. It does not produce a rectangle. – ImportanceOfBeingErnest Jun 01 '18 at 15:49
Yes, the result of a function applied over an array is an array, so the way you are using `fill_between` works but this is not pointing the problem in the OP. – Jacques Gaudin Jun 01 '18 at 15:50
This answer seems to pretty blindly copied from [here](https://stackoverflow.com/a/30580669/4124317). – ImportanceOfBeingErnest Jun 01 '18 at 21:29
It wasn't copied from anywhere other than my notes contained in one of my Jupyter Notebooks. I'll happily post the notebook somewhere you suggest (It contains other things too. – Paula Thomas Jun 01 '18 at 21:34

Shade area between 2 y coordinates in matplotlib

4 Answers4