MATLAB convert from struct to table and ouput as csv - matlab

Question

As part of an image processing pipeline using 'regionprops' in Matlab I generate the struct:
vWFfeatures =
1631x1 struct array with fields:
Area
Centroid
MajorAxisLength
MinorAxisLength
Eccentricity
EquivDiameter
Where 'Centroid' is a Vector containing [x, y] for example [12.4, 26.2]. I would like to convert this struct to a table and save as a CSV file. The objective is to separate the 'Centroid' vector into two columns in the table labelled Centroid_X and Centroid_Y for example. I am not sure how to achieve this.
So far I have investigated using the 'struct2table' function. This ouputs the 'Centroid' as one column. In addition when I try to assign the output to a variable I get an error:
table = struct2table(vWFfeatures)
Error using struct2table
Too many output arguments.
I cannot understand this, any help please?

Answer 1

Since the original struct2table isn't available to you, you might want to implement specifically the behavior you're trying to achieve yourself.
In this case, this means extracting the values you want to save, (split the array,) then save the data:
data_Centroid = vertcat(vWFfeatures.Centroid); %// contains the centroid data
Centroid_X = data_Centroid(:,1); %// The first column is X
Centroid_Y = data_Centroid(:,2); %// the second column is Y
csvwrite('centroid.csv',data_Centroid); %// writes values into csv
If you want column headers in your csv, it gets complicated because csvwrite can only handle numeric arrays:
celldata = num2cell(num2str(data_Centroid)); %// create cell array
celldata(:,3) = celldata(:,4); %// copy col 4 (y data) into col 3 (spaces)
for i=1:length(celldata)
celldata{i,2} = ','; %// col 2 has commas
celldata{i,4} = '\n'; %// col 4 has newlines
end
celldata = celldata'; %'// transpose to make the entries come columnwise
strdata = ['Centroid_X,Centroid_Y\n',celldata{:}]; %// contains all as string
fid = fopen('centroid.csv','w'); % writing the string into the csv
fprintf(fid,strdata);
fclose(fid);

Answer 2

This is how I solved it in the end: extracted each field from struct used horzcat to join into a new array then defined headers and used csvwrite_with_headers, to ouput to csv.
wpbFeatures = regionprops(vWFlabelled, 'Area','Centroid', 'MajorAxisLength', 'MinorAxisLength', 'Eccentricity', 'EquivDiameter');
wpbArea = vertcat(wpbFeatures.Area);
wpbCentroid = vertcat(wpbFeatures.Centroid);
wpbCentroidX = wpbCentroid(:,1);
wpbCentroidY = wpbCentroid(:,2);
wpbFeret = max(imFeretDiameter(vWFlabelled, linspace(0,180,201)), [], 2);
wpbMajorAxisLength = vertcat(wpbFeatures.MajorAxisLength);
wpbMinorAxisLength = vertcat(wpbFeatures.MinorAxisLength);
wpbEccentricity = vertcat(wpbFeatures.Eccentricity);
wpbEquivDiameter = vertcat(wpbFeatures.EquivDiameter);
wpbFeatures = horzcat(wpbArea, wpbCentroidX, wpbCentroidY, wpbFeret, wpbMajorAxisLength, wpbMinorAxisLength, wpbEccentricity, wpbEquivDiameter);
headers = {'Area','CentroidX','CentroidY', 'Feret', 'MajorAxisLength', 'MinorAxisLength', 'Eccentricity', 'EquivDiameter'};
csvwrite_with_headers(strcat(PlateName, '_ResultsFeatures.csv'),wpbFeatures,headers);