fitting data form a matrix using loops

Question

federico drudi 2022-9-19

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此问题的直接链接

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评论： federico drudi 2022-9-20

hello,

I made the following chart with averages, error bars and fittings starting from my data set. It took me some time as I am quite new to Matlab, but I know I did it wrong. I should be using loops but I have tried several times with no success.

Can someone please help me to understand it better?

Thank you very much!!!

d=readmatrix("shear_Stress_more.csv");
Error using readmatrix
Unable to find or open 'shear_Stress_more.csv'. Check the path and filename or file permissions.
ctrl = mean(d(:,2:5),2);
pef = mean(d(:,6:9),2);
USa = mean(d(:,10:11),2);
USb = mean(d(:,12:13),2);
enz = mean(d(:,14:17),2);
medie=[ctrl pef USa USb enz];
st_ctrl = std(d(:,2:5),0,2);
st_pef = std(d(:,6:9),0,2);
st_USa = std(d(:,10:11),0,2);
st_USb = std(d(:,12:13),0,2);
st_enz = std(d(:,14:17),0,2);
stdev = [st_ctrl st_pef st_USa st_USb st_enz];
ft = fittype('a+(b-a)*exp(-c*x)', ...
    'dependent',{'y'}, ...
    'independent',{'x'}, ...
    'coefficients',{'a','b','c',});
hold on 
[f,gof] = fit(d(:,1),medie(:,1), ft,'StartPoint',[3, 2, 0.01]);
errorbar(d(:,1),medie(:,1),stdev(:,1));
plot(f);
[f2,gof2] = fit(d(:,1),medie(:,2), ft,'StartPoint',[3, 2, 0.01]);
errorbar(d(:,1),medie(:,2),stdev(:,2));
plot(f2);
[f3,gof3] = fit(d(:,1),medie(:,3), ft,'StartPoint',[3, 2, 0.01]);
errorbar(d(:,1),medie(:,3),stdev(:,3));
plot(f3);
[f4,gof4] = fit(d(:,1),medie(:,4), ft,'StartPoint',[3, 2, 0.01]);
errorbar(d(:,1),medie(:,4),stdev(:,4));
plot(f4);
[f5,gof5] = fit(d(:,1),medie(:,5), ft,'StartPoint',[3, 2, 0.01]);
errorbar(d(:,1),medie(:,5),stdev(:,5));
plot(f5);
xlabel({'Time t [s]'});
ylabel({'Shear stress σ [Pa]'});
title({''});
legend('Control','PEF','USa','USb','Enzyme');
hold off

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Answer 1

Walter Roberson 2022-9-19

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You do not need all those variables at the same time, not for the purpose of the plot. You could look

for K = 1 : 5
    start = (K-1)*4 + 2;
    stop = start + 3;
    thisdata = data(:,start:stop);
    m = mean(thisdata,2);
    s = std(thisdata);
    [f, gof] = fit(d(:,1), m, ft, 'StartPoint', [3, 2, 0.01]);
    errorbar(d(:,1), m, s);
    h(K) = plot(f);
    hold on
end
hold off
xlabel({'Time t [s]'});
ylabel({'Shear stress σ [Pa]'});
title({''});
legend(h, {'Control','PEF','USa','USb','Enzyme'});

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federico drudi 2022-9-20

Thanks a lot, after a few changes it works perfectly and most importantly I am starting to understand this looping thing, really helpful.

Thanks again!

Cheers!!

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Answer 2

dpb 2022-9-19

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No real deal...your first part is somewhat more of a pain since you're averaging over a variable number of columns -- if it's a one-time exercise, I'd probably basically leave it along and only deal with it further if have to change these column IDs manuall

d=readmatrix("shear_Stress_more.csv");
% build summary data arrays
davg=[mean(d(:,2:5),2) mean(d(:,6:9),2) mean(d(:,10:11),2) mean(d(:,12:13),2) mean(d(:,14:17),2)];
dstd=[std(d(:,2:5),2)  std(d(:,6:9),2)  std(d(:,10:11),2)  std(d(:,12:13),2)  std(d(:,14:17),2)];
ft = fittype('a+(b-a)*exp(-c*x)', ...
                'dependent',{'y'}, ...
                'independent',{'x'}, ...
                'coefficients',{'a','b','c',});
hold on 
% build fit across columns
for i=1:size(davg,2);
  [f{i},gof{i}] = fit(d(:,1),davg(:,i),ft,'StartPoint',[3, 2, 0.01]);
  errorbar(d(:,1),davg(:,i),dstd(:,i));
  plot(f{i})
end
xlabel({'Time t [s]'});
ylabel({'Shear stress σ [Pa]'});
title({''});
legend('Control','PEF','USa','USb','Enzyme');
hold off