Contour Plotting matrix size issue

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?

[Walter Roberson]

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]

I don't know. Where is your call to the contour() function or the plot() function?

[Kelly]

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')

Answer 1

[Walter Roberson]

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?

[Kelly]

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')