put me out of my misery
1 view (last 30 days)
Show older comments
Rizwana
on 31 Jan 2014
Commented: Bjorn Gustavsson
on 3 Feb 2014
i have 3 matrices..
x = 1 * 264;
y = 1* 264;
z = 1 * 264;
contour(x,y,z) % error z must be 2* 2 or more
hence i did
[X,Y] = meshgrid(x,y); Z =griddata(x,y,z,X,Y);
contour(X,Y,Z) is giving some weird plot. Not desirable.
Now how to do it...
2 Comments
Iain
on 31 Jan 2014
What are you trying to plot?
contour(x,y,z) is expecting x to be a vector with n elements, y a vector with m elements, and z to be n by m (or is it m by n)
Accepted Answer
Bjorn Gustavsson
on 31 Jan 2014
Edited: Bjorn Gustavsson
on 31 Jan 2014
qwe = xlsread('yourfile.xls');
scatter(qwe(:,1).*cos(qwe(:,2)*pi/180),...
qwe(:,1).*sin(qwe(:,2)*pi/180),15,...
(qwe(:,3)-min(qwe(:,3)))*5+5,'filled')
So there you see some odd spots (sensor faulty or something?). At least easy to reinterpolate outside that region:
X = 24.7:0.1:27;
Y = 0:0.1:5;
[X,Y] = meshgrid(X,Y);
Z = griddata(qwe(:,1).*cos(qwe(:,2)*pi/180),...
qwe(:,1).*sin(qwe(:,2)*pi/180),qwe(:,3),X,Y);
% Or any of the newer variants like Walter suggested.
% do the contour:
hold on
contour(X,Y,Z,1.25:0.025:max(qwe(:,3)),'b')
HTH
2 Comments
Bjorn Gustavsson
on 3 Feb 2014
Yes, the trigonometric functions work on radians. You'd be better off learning to use radians.
More Answers (3)
Mischa Kim
on 31 Jan 2014
Rizwana, first option works just fine. Make sure that Z is an mxn matrix, where m and n are the length of the two vectors x and y. meshgrid , e.g., generates an appropriate grid.
x = rand(10,1);
y = rand(10,1);
[X,Y] = meshgrid(x,y);
Z = sin(X)+cos(X+Y);
figure
contour(X,Y,Z)
or see the documentation.
3 Comments
Mischa Kim
on 31 Jan 2014
The contour plot is more of a 3D type plot, where the dependent variable (Z) depends on two variables (X, Y). So it is not quite clear to me what you would like to achieve.
Iain
on 31 Jan 2014
Edited: Iain
on 31 Jan 2014
Looks like you actually want: plotyy or subplots:
plotyy(x,y,x,z) % plot angle against radius on the left hand y axis, and pressure against radius on the right hand y axis.
subplot(211)
plot(x,y)
subplot(212)
plot(x,z)
or
subplot(121)
plot(x,y)
subplot(122)
plot(x,z)
obviously, switch the x,y,z's around to plot against what you want to. - contour plots are only valid for 2-D signals, and you've only got 3 1D signals.
3 Comments
Iain
on 31 Jan 2014
Is circumferential pressure supposed to be a function of angle and radius?
If radius has "n" elements, and you have "m" angles, then you should get "n x m" pressures, and not have all three as being vectors.
For example, with a trivial function I know is wrong:
x= 0:0.1:1;
y= 0:36:360;
z = x' * y;
contour(x,y,z)
would work.
Walter Roberson
on 31 Jan 2014
7 Comments
Walter Roberson
on 31 Jan 2014
It appears that TriScatteredInterp appeared in R2009a. griddata() does exist in your release though.
See Also
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!