Contour Plotting matrix size issue

2013 2 15
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I am trying to plot computations using the contour plot, but am not sure how to because my z variable is the computation results and the dimensions are larger than y and x.
b = [0.1, 1.0, 10, 100];
R = (1:0.2:5);
theta = 45;
[F] = ratio_rp_bf(b,R,theta); 5x21
x = R.*cos(theta); 1x21
y = R.*sin(theta);1x21
z = [F];
Am I trying to plot the wrong things?

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Walter Roberson
Walter Roberson 2013-2-15
I notice your b is length 4, but your F is 5 in the first dimension ? Is the rule that your F's first dimension is 1 more than length(b) ?
Image Analyst
Image Analyst 2013-2-15
I don't know. Where is your call to the contour() function or the plot() function?
Kelly
Kelly 2013-2-15
编辑：Kelly 2013-2-15
this is my function
function [F] = ratio_rp_bf(b,R,theta)
for i = 1:length(b)
for r = 1:length®
F(i,r) = (16/3).*(1./b(i)).*(1./R(r)).^3.*sqrt((1./R(r)).^4-2.*(1./R(r)).^2.*cos(2.*theta)+1);
end
end
this is as far as I've gotten in terms of plotting a 2x2 subplot, everytime I do another subplot it looks exactly the same. I'm trying to get it to plot for each b value.
b = [0.1, 1.0, 10, 100]; R = (1:1.2:5); theta = atan(R/b); [F] = ratio_rp_bf(b,R,theta);
x = R.*cos(theta);
y = R.*sin(theta);
z = F;
figure(1)
subplot(2,2,1)
contour(x,y,z)
grid on
xlabel('b/D50')
ylabel('radii')
title('Radial Pressure vs. Bed Forces')

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Walter Roberson
Walter Roberson 2013-2-15

0 个投票

When you use
contour(XVALUES, YVALUES, ZVALUES)
then XVALUES should be a vector of length size(ZVALUES,1), and YVALUES should be a vector of length size(YVALUES,2). Your Z is 5 x 21, and your R is of length 21 (so your y is too), but you do not appear to have any variable of length 5 to supply for XVALUES.
Are you sure you want to contour? And not that you want to plot 5 lines in 3 space?

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Kelly
Kelly 2013-2-15
this is my function
function [F] = ratio_rp_bf(b,R,theta)
for i = 1:length(b)
for r = 1:length®
F(i,r) = (16/3).*(1./b(i)).*(1./R(r)).^3.*sqrt((1./R(r)).^4-2.*(1./R(r)).^2.*cos(2.*theta)+1);
end
end
this is as far as I've gotten in terms of plotting a 2x2 subplot, everytime I do another subplot it looks exactly the same. I'm trying to get it to plot for each b value using contour.
b = [0.1, 1.0, 10, 100]; R = (1:1.2:5); theta = atan(R/b); [F] = ratio_rp_bf(b,R,theta);
x = R.*cos(theta);
y = R.*sin(theta);
z = F;
figure(1)
subplot(2,2,1)
contour(x,y,z)
grid on
xlabel('b/D50')
ylabel('radii')
title('Radial Pressure vs. Bed Forces')

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