How to convert a cell array of singles and doubles to an array of a single type (double)?

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Minh Tran 2018-9-19

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评论： Minh Tran 2018-9-25

I queried a database for an array of numerical values. The query is a function call that returns a struct of different cell-arrays (one of which is "struct.speed"). I tried use cell2mat() to convert each cell element to an array (of a uniform type, which is what cell2mat does) but I found out that some cells contained `singles` while others contained `doubles` (doubles where there were NaN values).

Attached is "struct.speed" (as well as the original struct) and the call I used to check the type of each cell element was:

cellfun(@class, struct.speed(:,1), 'UniformOutput', false);

I tried calling typecast and it produced an error I didn't understand:

EDITED: Oh right -- struct.speed(:,1) is a cell array and type cast only works on numeric values (or arrays of them).

K>> typecast(struct.speed(:,1), 'double')
??? Error using ==> typecastc
The first input argument must be a full, non-complex numeric value.
Error in ==> typecast at 31
  out = typecastc(in, lower(datatype));

I need to do the type casting because I wanted to use slice-notation to assign the result to another struct "WHBB.Speed":

WHBB.Speed(:, bin) = struct.speed(:,1); % Error: Conversion to double from cell is not possible

The above statement works for slices of struct.speed that doesn't contain a mix of NaN's and numeric values (slices of all NaNs or slices of all doubles)

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Stephen23 2018-9-19

Do NOT call your variable struct, as this shadows the inbuilt struct function.

Minh Tran 2018-9-25

Thank you for pointing that out.

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Answer 1

Stephen23 2018-9-19

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编辑：Stephen23 2018-9-19

在 MATLAB Online 中打开

Assuming that each cell contains a scalar value:

cellfun(@double,myStruct.speed)

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Answer 2

Minh Tran 2018-9-19

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编辑：Minh Tran 2018-9-19

在 MATLAB Online 中打开

A solution I just came up with that is kind of clunky:

result = NaN(size( struct.speed(:,1) )); % Preallocate a vector of NaNs
for i=1:length(struct.speed(:,1))
   result(i) = double( struct.speed{i,1} ); % Element wise conversion of all elements to doubles
end