# How to fit a particular analytical function while optimising its parameters to a histogram for different data sets in a loop in Matlab?

조회 수: 2 (최근 30일)
JOYA GHOSH DASTIDER 2022년 11월 12일
댓글: JOYA GHOSH DASTIDER 2022년 11월 23일
Hi,
I am trying to fit a particular analytical function to histogram of a dataset. The parameters of the function is being optimised using lsqcurvefit command of Matlab. When I am trying for a single data set, its giving right curve. But when I am trying to put it in a loop to fit several datasets such that each time it will take one dataset and fit the function with optimized parameters to its histogram and then go to the next dataset and do the same job, it is giving wrong curve.
I am suspecting that somehow it is taking garbage values while plotting the function.
thank you.
d=dir('latlong*.csv');
n=length(d);
data=cell(n,1);
for i = 0:2
for j=0:0
a = data{j*70 + i+1};
b(:,1) = a(:,2);
k3=0;
for l=1:8831
if b(l,1)>=0.001
k3=k3+1;
end
end
z=zeros(k3,1);
k3=0;
for l=1:8831
if b(l,1)>=0.001
k3=k3+1;
z(k3,1)=b(l,1);
end
end
figure(i+1);
hold on
h=histogram(z,1000,'Normalization','pdf');
no=h.NumBins;
counts=zeros(no,1);
counts(:,1)=h.Values;
edge=zeros(no+1,1);
edge(:,1)=h.BinEdges;
edge=edge(2:end,1);
Fun3=@(q,edge) ((1./(edge.*q(2).*sqrt(2*pi))).*exp(-((log(edge)-q(1)).^2)./(2*q(2)^2)));
q0=[2,2];
q(i+1,:) = lsqcurvefit(Fun3,q0,edge,counts);
plot(edge,Fun3(q,edge));
hold off
xlabel('Observation')
ylabel('Probability Density')
legend('histogram','log')
end
end

댓글을 달려면 로그인하십시오.

### 답변 (1개)

Brian 2022년 11월 18일
Hello Joya,
I refactored your code to get a better idea of what it was doing, and there seem to be two issues. The main issue is that on line 39 you call "Fun3" with "q" instead of "q(i+1,:)". The second issue is that "csvread" is prepending a zero to your data. The "csvread" function is not recommended and it is recommended to use "readmatrix" or "readtable" instead.
d=dir('latlong*.csv');
n=length(d);
data=cell(n,1);
q=zeros(n,2);
for i = 1:n
z=data{i}.precipitation(data{i}.precipitation >= 0.001);
figure(i);
hold on
h=histogram(z,1000,'Normalization','pdf');
no=h.NumBins;
counts=h.Values';
edge=h.BinEdges(2:end)';
Fun3=@(q,edge) ((1./(edge.*q(2).*sqrt(2*pi))).*exp(-((log(edge)-q(1)).^2)./(2*q(2)^2)));
q0=[2,2];
q(i,:)=lsqcurvefit(Fun3,q0,edge,counts);
plot(edge,Fun3(q(i,:),edge));
hold off
xlabel('Observation')
ylabel('Probability Density')
legend('histogram','log')
end
Hope this helps, let me know if I misunderstood anything.
##### 댓글 수: 1이전 댓글 -1개 표시이전 댓글 -1개 숨기기
JOYA GHOSH DASTIDER 2022년 11월 23일
Thank you for your reply and really sorry for being late in acknowledging .
I also figured out the problem of not using "q(i+1,:)".

댓글을 달려면 로그인하십시오.

### 카테고리

Help CenterFile Exchange에서 Get Started with Curve Fitting Toolbox에 대해 자세히 알아보기

### Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by