I have line and want to colour the area behind the line (beyond the x axis) how can I do this

I have a line in the format y= mx+c, and I want to shade/colour the area 'behind' the line depending on the direction of my line. I can only see functions that shade/colour the axis from line to x axis. Is there a way of doing what I am describing

[Image Analyst]

How many colors might that be? There are an infinite number of directions your line can point. Please attach 2 or 3 examples.

[Dyuman Joshi]

Check out

fill

patch

area

[Adam Danz]

Could you clarify what behind the line means?

[Katherine]

So I have a line that could be infitely long (but isn't for the purposes of plotting quickly) that will essentially divide the graph

e.g. y= 3x+ 2

I want the ability to choose to shade/fill 'behind' the line. Which I understand is kind of arbitrary. The purpose is to show a user they should not plot in that area, so I will be using a function/ have some code that gives me the ability to choose/define what 'behind' is.

Most functions I have seen just shapes up to an axis, I want to shade the entire underneath or the entire above the line depending on my needs.

Does that make more/better sense?

[Image Analyst]

Not really? Did you expand the comments to see all of them or only see the last one?

[Adam Danz]

Thanks @Katherine, that makes sense to me. Looks like @Star Strider's answer addresses your question.

Answer 1

[Star Strider]

I am not completely certain what ‘behind’ the line means, however from your comments with respect to the x-axis, I guess that you mean fro the y-axis to the line.

If so, try this —

x = linspace(0, 10).';
m = randn

m = -0.8135

c = randn

c = 0.4800

y = m*x + c;

figure
plot(x, y)
hold on
patch([x; zeros(size(x))], [y; flip(y)], 'r', 'FaceAlpha',0.5, 'EdgeColor','none')
hold off

m = randn

m = 1.6675

c = randn

c = -0.4378

y = m*x + c;

figure
plot(x, y)
hold on
patch([x; zeros(size(x))], [y; flip(y)], 'r', 'FaceAlpha',0.5, 'EdgeColor','none')
hold off

Please clarify if you intend something else.

EDIT — (23 Nov 2023 at 15:27)

Added second plot with different parameters.

EDIT — (23 Nov 2023 at 17:25)

Added ‘Entire Underneath the Line’ and ‘Entire Above the Line’ in the following code sections —

x = linspace(0, 10).';
m = randn

m = -0.0184

c = randn

c = 0.8392

y = m*x + c;

figure
plot(x, y)
hold on
patch([x; flip(x)], [y; zeros(size(y))+min(ylim)], 'g', 'FaceAlpha',0.5, 'EdgeColor','none')
hold off
title(sprintf('Entire Underneath the Line\ny = %.3f*x %+.3f', m,c))

m = randn

m = 1.4742

c = randn

c = -1.7464

y = m*x + c;

figure
plot(x, y)
hold on
patch([x; flip(x)], [y; zeros(size(y))+max(ylim)], 'g', 'FaceAlpha',0.5, 'EdgeColor','none')
hold off
title(sprintf('Entire Above the Line\ny = %.3f*x %+.3f', m,c))

.