Asked by Ugur Acar
on 9 Oct 2019

Easy question for advanced users, big question for a beginner like me.

I want to put an empty value or no value into a numeric matrix.

As an example;

if true

for n=1:4;

If %some condition is satisfied%

Data(n,1)= % a numeric value like 4%

Else

Data(n,1)= % put nothing in this row %

end

End

end

Something like this,

Data(1,1)=3

Data(2,1)=4

Data(3,1)= no value,it exist but no value in it

Data(4,1)=5

Answer by meghannmarie
on 9 Oct 2019

Accepted Answer

How about putting a NaN in it?

Data(n,1)= NaN;

John D'Errico
on 9 Oct 2019

In older versions of MATLAB, you could find tools like nansum, which will compute a sum, while omitting the NaN elements. (nansum is in the stats toolbox.) Hiwever in present day MATLAB, you will find an option to omit the NaNs in sum.

'omitnan' - the sum of a vector containing NaN values

is the sum of all its non-NaN elements. If all

elements are NaN, the result is 0.

However, you CANNOT put an empty value in an array. Arrays do not work like that. Arrays are rectangular things, with SOMETHING in every element. Nothing is not an option.

Ugur Acar
on 9 Oct 2019

Turlough Hughes
on 9 Oct 2019

You could sum the data in your array by excluding NaNs during summation:

sum(Data(~isnan(Data)))

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Answer by Ugur Acar
on 9 Oct 2019

Ugur Acar
on 9 Oct 2019

Thank you Steven, i guess what i was looking for is fillmissing function, i will try it

meghannmarie
on 9 Oct 2019

When you use sum or any other statistics use the nan flag if you do not want those considered:

S = sum(Data, 'omitnan')

if you want to interpolate at the nan values, you can get of an index to all the nan values by using isnan and using interp1:

nan_idx = isnan(Data);

x = 1:numel(Data);

Data(nan_idx) = interp1(x(~nan_idx), Data(~nan_idx),x(nan_idx));

Ugur Acar
on 9 Oct 2019

Nan flag will solve the problem i believe thanks meghannmarie

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