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In Matlab can I directly modify a value in a when the value is the element of an array?

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Joseph Koval
Joseph Koval on 4 Dec 2019
Answered: Adam Danz on 4 Dec 2019
I'm wondering if this syntax is possible? Specifically, I want to increment the first element of the array which is the number 3, cooresponding to the first value that the key 'Li' points to. Specifically, I'm asking about the line "M('Li')(i) = M('Li')(i) + 1"
keySet = {'Li','Jones','Sanchez'};
testLi = [3 4 5];
testJones = [27 3.92 6.4 8.21];
testSanchez = 'C:\Tests\Sanchez.dat';
valueSet = {testLi,testJones,testSanchez};
M = containers.Map(keySet,valueSet,'UniformValues',false)
M('Li')(i) = M('Li')(i) + 1
I know this doesn't work, it throws an error. Can this be done without code that looks like this:
hold = M('Li')
hold(1) = hold(1) + 1
M('Li') = hold


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Accepted Answer

Adam Danz
Adam Danz on 4 Dec 2019
You could add a local function at the bottom of the m-file that does the dirty work.
M = plusOne(M,'Li',i);
function mapObj = plusOne(mapObj,key,idx)
% This function merely adds 1 to mapObj(key)(idx)
% mapObj is the handle to the map container
% key is a char array naming the key
% idx is a positive integer identifying which value to add one to
v = zeros(size(mapObj(key)));
v(idx) = 1;
mapObj(key) = mapObj(key) + v;
end % 'end' may or may not be needed


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