Plotting 2d data

Haven't touched Matlab in over two years, trying to create a graph plotting my answers. I'm getting an error "Index exceeds the number of array elements (1)."

%loop for thickness
for i = 3 : 1 : 10
    
    %loop for number of fins
    for j = 8 : 1 : 12
        m(i) = sqrt((2*ho)/(k*t(i)/1000)); % m^-1
        At(i,j) = fins(j)*Af+((2*pi*r2)-(fins(j)*t(i)/1000)); %m
        n_o(i,j) = 1-(((fins(j)*Af)/At(i,j))*(1-(tanh(m(i)*(r3-r2))/(m(i)*(r3-r2))))); 
        R_to(i,j) = 1/(n_o(i,j)*ho*At(i,j)); % m*K/W
        R_t(i,j) = R_conv + R_cond +R_to(i,j); % m*K/W
        q(i,j) = (delta_T)/(R_t(i,j)); % W/m
        plot(j,q(i,j),'b-',linewidth',2);
        hold on
    end
end

plot(fins,q,'r.','markersize',20,'linewidth',2);
set(gca,'fontsize',16,'fontweight','bold')
title('Heat Rate increase as fins and thickness increases');
xlabel('Number of Fins','fontsize',16);
ylabel('Heat Rate (W)','fontsize',16);

Answer 1

[Walter Roberson]

t = 0.003 is a scalar, but you index t(i)

Caution: your i and j are scalars, so plot(j, q(i,j), 'b-') is going to try to plot a single point. plot() only ever draws a line you pass it two adjacent finite values in a single call. Your plot() call is not going to plot anything. If you were to alter the 'b-' to 'b*-' then it would at least place markers at the single points that it draws.

[madhan ravi]

Even fins is a scalar.

[darkphotonix]

Gotcha, I completey spaced on that. How would I then seperate the plot points for each thickness on a graph

[Walter Roberson]

Parts of the code have mysteriously vanished and due to an allergy flare I don't seem to have successfully memorized it before it changed.