How to calculate the mean for the number of occurances

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johnson saldanha 2018-12-7

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编辑： dpb 2018-12-9

suppose i have a cell C where

C{1,1}= ( 2 2 2 2 3 3 4 4 5);
C{2,1}=(3 4 4 4 5);
C{3,1}=(4 5);

and so on

i want the output as

x = (2 2 2 2 3 3 4 4 5);

the output should be the value which occurs the mean number of times of the occurances in the input. if the value is a decimal then it can rounded to a greater whole number for ex: the value 3 occurs twice in first cell and once in second cell. 2+1/2= 1.5 can be rounded to 2. so it occurs twice in the output.

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Answer 1

dpb 2018-12-7

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https://ww2.mathworks.cn/matlabcentral/answers/434421-how-to-calculate-the-mean-for-the-number-of-occurances#answer_351069

在 MATLAB Online 中打开

u=unique([C{:}]);
n=cell2mat(cellfun(@(x) histc(x,u),C,'uni',0));
n(n==0)=nan;
x=cell2mat(arrayfun(@(x,n) repmat(x,1,n),u,round(nanmean(n)),'uni',0));
>> x =
     2     2     2     2     3     3     4     4     5
>> 

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dpb 2018-12-7

编辑：dpb 2018-12-7

在 MATLAB Online 中打开

Need to see what you are using specifically for C, then...works fine for a 1D cell array of double vector arrays for me--

>> C
C =
  3×1 cell array
    {1×9 double}
    {1×5 double}
    {1×2 double}
>> ([C{:}])
ans =
     2     2     2     2     3     3     4     4     5     3     4     4     4     5     4     5
>> unique([C{:}])
ans =
     2     3     4     5
>> 

The colon operator inside the [] to catenate the list returns all elements of C as a row vector and unique subsequently returns the subset vector.

How is your C cell array different than above?

NB: If don't make the orientation of the vectors you incorporate into C consistent, however, that will cause such an error. If take the above and add

>> C{4,1}=[4 5].';
>> u=unique([C{:}]);
Error using horzcat
Dimensions of matrices being concatenated are not consistent. 
>> 

The problem here is, of course, that the last cell is a column vector instead of a row vector.

>> C
C =
  4×1 cell array
    {1×9 double}
    {1×5 double}
    {1×2 double}
    {2×1 double}
>> 

so the input doesn't match the expectations. In that case you would need to write

u=unique(cat(1,C{:}));

to catenate vertically; the [] Matlab idiom does catenation of the list elements horizontally and when there are differing number of elements on a row, that fails.

johnson saldanha 2018-12-9

all are column vectors. theres no row vector

dpb 2018-12-9

编辑：dpb 2018-12-9

That's not what the error message says... :)

If the vectors inside the initial cell array are columns instead of rows as your initial example, then as above you'll have to first cat(1,...) them, but then the counts array will end up being a column vector instead of the 2D array because cellfun will just concatenate those columns into one long (column) vector instead of concatenating the rows vertically and you've thus lost the orientation that lets nanmean know how to average across the cells as is the whole end objective.

Probably the easiest way to code it would be to transpose the argument of the histc function inside the anonymous function so it is again a row vector there as needs must be...otherwise, you've got much more painful gyrations to build the necessary array shape.

Step through each step at the command line for a (smallish) example so you can see the results of each operation and get the proper orientation for the job.

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