Saving output values from a function into an array (to plot later)

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Sid Halder
Sid Halder 2019-12-18
评论： Sid Halder 2019-12-18
So I have written a loop that runs a function for a given m to give a specific time_hours value (for that given m). The program works and I get all the values I need, but how would I save these values in an array to plot against m later on? I'm not sure how this would work as I have used fzero to calculate the time_hours values on each iteration and fzero values cannot be indexed? Thanks for any help, here is my code:
alpha = 0.7e-7; rho = 0.1 .^(1/3); %m = [4:0.1:8];
for m = 4:0.1:8
[term, scarysum, summation_t, f, time_seconds, time_hours] = tcalc(alpha, rho, m);
end
function [term, scarysum, summation_t, f, time_seconds, time_hours] = tcalc(alpha, rho, m)
scarysum = 0;
for k = 1:30
syms t
term = ((-1).^(k-1))./k .* sin(k.*pi.*rho) .* exp((-1 .* k.^2 .* pi.^2 .*alpha.*(1360.*pi).^(2/3).*t)./m.^(2/3));
scarysum = scarysum + term;
end
summation_t = matlabFunction(scarysum);
f = @(t) (2./(pi*rho) .* (summation_t(t))) - 0.7125;
time_seconds = fzero(f,14400);
time_hours = time_seconds ./ 3600;
disp(time_hours)
end

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采纳的回答

Allen
Allen 2019-12-18
编辑：Allen 2019-12-18
If your function is returning scalar values that are being overwritten during each iteration of your for-loop, try the following as a replacement to your for-loop.
[term, scarysum, summation_t, f, time_seconds, time_hours] = arrayfun(@(m) tcalc(alpha, rho, m), 4:0.1:8);
% This is essentially the same as rewriting the for-loop to something like this, which changes the size
% of the output variables each iteration and appends the new value to the end of each variable.
rng = 4:0.1:8;
for m = length(rng)
[term(m), scarysum(m), summation_t(m), f(m), time_seconds(m), time_hours(m)] = tcalc(alpha, rho, rng(m));
end
  1 个评论
Sid Halder
Sid Halder 2019-12-18
Thank you so much! It's honestly so convenient that arrayfun exists, perfect function to use in my case. Ran into a few problems with arrayfun as my output variables contained exponential terms (which aren't scalar) so MATLAB had issues creating the new arrays but I think I've sorted it all out. Thanks once again.

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更多回答（1 个）

Cameron B
Cameron B 2019-12-18
options = optimset('PlotFcns',@optimplotfval);
scarysum = 0;
for k = 1:30
syms t
term = ((-1).^(k-1))./k .* sin(k.*pi.*rho) .* exp((-1 .* k.^2 .* pi.^2 .*alpha.*(1360.*pi).^(2/3).*t)./m.^(2/3));
scarysum = scarysum + term;
end
summation_t = matlabFunction(scarysum);
f = @(t) (2./(pi*rho) .* (summation_t(t))) - 0.7125;
[time_seconds,fval,exitflag,output] = fzero(f,14400,options);
time_hours = time_seconds ./ 3600;
disp(time_hours)
fig = gcf;
dataObjs = findobj(fig,'-property','YData');
y1 = dataObjs(1).YData;
x1 = dataObjs(1).XData;
You'll have to save y1 and x1 each time, but that's how you'd extract the data.

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