MATLAB: How to sort a structure array based on a specific field

MATLAB

How do we sort a structure array based on a specific field?

Best Answer

We have an instruction blog on how to do that in older versions of MATLAB (before R2013b):

https://blogs.mathworks.com/pick/2010/09/17/sorting-structure-arrays-based-on-fields/

If you are using a MATLAB version newer than R2013b, you can take advantage of the "sortrows" function in tables for a simpler workflow:

>>  % suppose 's' is the struct array. 'DOB' is the field that contains date and time.
>>  T = struct2table(s); % convert the struct array to a table
>>  sortedT = sortrows(T, 'DOB'); % sort the table by 'DOB'
>>  sortedS = table2struct(sortedT) % change it back to struct array if necessary

Related Solutions

MATLAB: How to find duplicate values in a structure

Find below the function that takes structure "s" as input and gives you a cell array with duplicates. Please note that output of the below function would be a cell array. If you need a structure instead of cell array as output, please return the "newStruct" value in the below function.

    function finalDuplicatesCellArray = selectDuplicates(s)
        keys = fieldnames(s);
        values = struct2array(s);
        uniqueValues = unique(values);
        valueCounts = histcounts(values, length(unique(values)));
        idx = valueCounts > 1;
        duplicatedValues = uniqueValues(idx);
        duplicateValuesIndices = ismember(values,duplicatedValues, 'legacy');
        duplicateKeys = keys(duplicateValuesIndices);
        duplicateValues = values(duplicateValuesIndices);
        newStruct = struct;
        for ii = 1:length(duplicateKeys)
            newStruct.(char(duplicateKeys(ii))) = duplicateValues(ii);        
        end
         %Convert the newStruct to cell array
         valuesFinal = num2cell(duplicateValues');
         finalDuplicatesCellArray = [duplicateKeys,valuesFinal];   
    end

Input example: S.A = 1; S.C = 1; S.E = 1; S.F = 1;

Output: 4×2 cell array

    'A'    [1]
    'C'    [1]
    'E'    [1]
    'F'    [1]

MATLAB: How to use custom date labels for the x-axis in MATLAB plots

It is more convenient to format the tick labels using the "XTick", "XTickLabelMode" and "XTickLabel" properties of the axis object (vs. using "datetick" function):

>> figure
>> box on
>>
>> % Start, end and number of ticks...
>> startDate = 7.3457e+05;
>> endDate = 7.3458e+05;
>> numbertick = ceil(endDate - startDate);
>>
>> % Plot them
>> xData = linspace(startDate, endDate, numbertick);
>> plot(xData,ones(size(xData)));
>>
>> %%Modify the axes properties
>> set(gca, 'XTick',xData)
>> set(gca, 'TickDir', 'out');
>> set(gca, 'XTickLabelMode', 'auto');
>>
>> % Modifying the labels
>> labels = get(gca, 'XTickLabel');
>>
>> for i = 1:length(labels)
>>     if i == 1 || i == ceil(length(labels)/2) || i == length(labels)
>>         labels{i} = datestr(xData(i), 'mm/dd');
>>     else
>>         labels{i} = '';
>>     end
>> end
>>
>> set(gca, 'XTickLabel', labels)

Best Answer

Related Solutions

MATLAB: How to find duplicate values in a structure

MATLAB: How to use custom date labels for the x-axis in MATLAB plots

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