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Get the mean and standard deviation of the lower half of the first mode of a bimodal distribution

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Hi, I have a bimodal distribution (in the form of a vector) from which I want to fit a gaussian distribution to the lower half of the first mode and calculate the mean and standard deviation of that distribution.
Any advice?

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Accepted Answer

Image Analyst
Image Analyst on 4 Sep 2020
Here is code that uses fitnlm() to fit two Gaussians, and one that fits multiple Gaussians.

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Stephen
Stephen on 4 Sep 2020
My Q doesn't apply to this specific thread (pls accept my apologies), but I don't know how else to contact Image Analyst. Some time back you helped out a user with a Q re: opening/closing an excel file from within MatLab. I'm having a devil of at time with the PlotInExcel function by Amit Doshi and am hoping you might shed some light. The problem is: I can't figure out how to save the file and quit Excel at the end of PlotInExcel. Consequently, I can't get back to my script. Excel just hangs open and I have to save/close it manually. Do you have any ideas? Any help would be greatly appreciated!
function PlotInExcel
x= {1:10};
a= cell2mat(x);
y= {1:10};
b= cell2mat(y);
%............plotting..............................................................................................
plot(a,b);
xlabel('X Values');
ylabel('Y Values');
print -dmeta; %.................Copying to clipboard
FILE = 'C:\DATA.xlsx';
Range='OX14';
%.............excel COM object............................................................................
Excel = actxserver ('Excel.Application');
Excel.Visible = 1;
if ~exist(FILE,'file')
ExcelWorkbook=Excel.Workbooks.Add;
ExcelWorkbook.SaveAs(FILE);
ExcelWorkbook.Close(false);
end
invoke(Excel.Workbooks,'Open',FILE); %Open the file
ActiveSheet = Excel.ActiveSheet;
ActiveSheetRange = get(ActiveSheet,'Range',Range);
ActiveSheetRange.Select;
ActiveSheetRange.PasteSpecial; %.................Pasting the figure to the selected location
%-----------------------------------end of function"PlotInExcel--------------------------------------
Image Analyst
Image Analyst on 6 Sep 2020
Stephen, add these lines:
Excel.ActiveWorkbook.Save;
Excel.Quit;
delete(Excel);
clear('Excel')
See attached utilities for Excel.

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More Answers (1)

Abdolkarim Mohammadi-Balani
Edited: Abdolkarim Mohammadi-Balani on 2 Sep 2020
You can first determine the elements that are in the lower half
LowerHalfMask = Data <= mean(Data);
Then calculate the statistics
LowerHalfMean = mean(Data(LowerHalfMask));
LowerHalfStd = std(Data(LowerHalfMask));
To fit a distribution, you can first collect the elements of the lower half
LowerHalfValues = Data(LowerHalfMask);
Then use the Curve Fitting App (type cftool in the command window).

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Audun Kvalvaag
Audun Kvalvaag on 4 Sep 2020
Thanks, I solved it by mirroring the lower half of the first mode with the flip function. I could then use this gaussian fit function: https://www.mathworks.com/matlabcentral/fileexchange/35122-gaussian-fit to get the mean and standard deviation.

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