# How can I plot the region for two inequalities?

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Matthew Morrison on 28 Jul 2016
Commented: Image Analyst on 19 Apr 2021
I'm looking to plot the two inequalities for the formula: abs(x+y+x.^2<3) and abs(y+x+y.^2<3)
with them both being on the same plot. How would I go about doing this please? Or any other similar example is fine.
##### 2 CommentsShowHide 1 older comment
Rena Berman on 30 Oct 2016
(Answers dev) restored the original question

Karan Gill on 29 Jul 2016
Here's how to numerically evaluate the conditions and visualize them.
v = -5:0.01:5; % plotting range from -5 to 5
[x y] = meshgrid(v); % get 2-D mesh for x and y
cond1 = x+y+x.^2 < 3; % check conditions for these values
cond2 = y+x+y.^2 < 3;
cond1 = double(cond1); % convert to double for plotting
cond2 = double(cond2);
cond1(cond1 == 0) = NaN; % set the 0s to NaN so they are not plotted
cond2(cond2 == 0) = NaN;
cond = cond1.*cond2; % multiply the two condaces to keep only the common points
surf(x,y,cond)
view(0,90) % change to top view
Image Analyst on 19 Apr 2021
The "cond" matrix is either 0 or nan, so why does it look curved/warped instead of flat?

### More Answers (2)

Image Analyst on 29 Jul 2016
You could do this:
r = -5:0.01:5; % plotting range from -5 to 5
[x, y] = meshgrid(r); % Get 2-D mesh for x and y based on r
condition1 = x+y+x.^2 < 3;
condition2 = y+x+y.^2 < 3;
output = ones(length(r)); % Initialize to 1
output(~(condition1 & condition2)) = 0; % Zero out coordinates not meeting conditions.
imshow(output, 'xdata', r, 'ydata', r); % Display
axis on;
##### 2 CommentsShowHide 1 older comment
Image Analyst on 5 Oct 2020
Try
axis ij;
after you've called imshow().

Anna on 20 Nov 2017
Is it possible to draw the region with a different color than black?