MATLAB: Logical indexing with a structure

indexlogical?MATLABstructstructure

I have a structure, "s", and I am trying to use logical indexing to create a new structure, "s1", for when the field, "field1", is equivalent to 1 and a new structure, "sc" for when the field, "field2", is equivalent to 'c'. How can I do this?

>> s = struct('field1', {1,2,3,4}, 'field2', {'ab', 'b', 'c', 'c'});

Best Answer

Logical indexing with structures is similar to other logical indexing in MATLAB. The one difference is when you are trying to use fields in the equivalence statement. This is because s.field1 has multiple outputs. To get around this, simply put brackets [] or {} around s.field1 in order to get one output that is an array or cell.

>> s1 = s([s.field1]==1);
>> sc = s(strcmp({s.field2}, 'c'))

Related Solutions

MATLAB: Is it possible to concatenate two structures in MATLAB 7.5 (R2007b)

If the structures have the same field names, you may contatenate them using [ ], HORZCAT or VERTCAT as follows:

S1 = struct('type', {'big1','little1'}, 'color', {'red1'}, 'x', {3 4})
S2 = struct('type', {'big2','little2'}, 'color', {'red2'}, 'x',{12,13})
% All of the following should work on these structs
[S1 S2]
[S1;S2]
horzcat(S1,S2)
cat(1,S1,S2)
cat(2,S1,S2)

The ability to concatenate two dissimilar structures (with different field names) is not available in MATLAB. For instance,

S1 = struct('type1', {'big1','little1'}, 'color1', {'red1'}, 'x1', {3 4})
S2 = struct('type2', {'big2','little2'}, 'color2', {'red2'}, 'x2',{12,13})

You may create a cell array of these structures,

S = {S1, S1}

Or, you may be able to do use the following approach to create a struct with a union of the field names. Any non-common fields will be set to [ ]

S = S1;
F = fieldnames(S2);
for i = length(S)+1:length(S)+length(S2)
      for j = 1:length(F)
          S(i).(F{j}) = S2.(F{j});
      end
end

MATLAB: How to create a pictogram in MATLAB

You can use "imread" and "image" in a a for-loop to create a pictogram.

>> x = [1 2 3 4];
>> y = [2 4 3 2];
>> im = imread('peppers.png');
>> figure
>> hold on
>> xPos = [1 0.1];
>> yPos = [1 0.1];
>> for i = 1:numel(x)
>>     xPos = xPos + 1;
>>     for j = 1:y(i)
>>         image(xPos, yPos, im)
>>         yPos = yPos + 1;
>>     end
>>     yPos = [1 0.1];
>> end

Best Answer

Related Solutions

MATLAB: Is it possible to concatenate two structures in MATLAB 7.5 (R2007b)

MATLAB: How to create a pictogram in MATLAB

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