MATLAB: Constructing matrix elements conditionally (and sequentially)

matrix manipulation

Hi,

I have two matrices of differing lengths:

A = [1 1 0 1 0 0 1 0 1 0 1] B = [25.4 17.3 11.6 9.2 14.3 15.0]

I want to construct a matrix (C) that is the same length of A, but the 1 values are sequentially replaced by those in matrix B to yield:

C = [25.4 17.3 0 11.6 0 0 9.2 0 14.3 0 15.0]

Can anyone direct me to any relevant functions/methods that can do this?

As an aside, sum(A)==length(B) in all cases. However, sum(A) and length(B) will both vary with each iteration.

Thank you immensely.

Dave

Best Answer

   C = zeros(size(A));
   C(A>0) = B;

(Note that this will give an error if your assumption that sum(A)==length(B) is not true.)

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MATLAB: Product of elementwise differences

Not much too this one.

fliplr(cumsum(diff([zeros(size(A,1)),fliplr(A)],1,2) .* diff([zeros(size(B,1)),fliplr(B)],1,2),2))

MATLAB: Changing header to csv using writetable

In R2016b, the variable names must be valid MATLAB variable names. (That changed in R2020a, so what you want to do would be permitted.)

The other problem you are having is that the dates in column #1 need to be a datetime array.

This does everything except use the variable names you want:

M = [19790101  7839.4  29.4  17.3  1.6  51.8  13.8  5.2 
     19790102  8046.4  30.1  17.5  0.1  45.2  16.2  4.9
     19790103  9018.2  27.6  13.5  0  40.9  14.3  5.2
     19790104  5359.4  21.8  14.4  0.2  61.5  8  4.9
     19790105  8145.9  26.4  13.6  0.7  52.2  11.2  3.8 ];
T1 = array2table(M);
DT = datetime(num2str(M(:,1)), 'InputFormat','yyyyMMdd');
T1.M1 = DT

producing:

T1 =
  5×8 table
        M1           M2       M3      M4     M5      M6      M7     M8 
    ___________    ______    ____    ____    ___    ____    ____    ___
    01-Jan-1979    7839.4    29.4    17.3    1.6    51.8    13.8    5.2
    02-Jan-1979    8046.4    30.1    17.5    0.1    45.2    16.2    4.9
    03-Jan-1979    9018.2    27.6    13.5      0    40.9    14.3    5.2
    04-Jan-1979    5359.4    21.8    14.4    0.2    61.5       8    4.9
    05-Jan-1979    8145.9    26.4    13.6    0.7    52.2    11.2    3.8

Change the variable names to versions of what you have that will work in R2016a. Even if you change them to what you want in the file, they will be changed to valid MATLAB variable names when you import it. Your only option is to upgrade to R2020a or later to use the variable names you want to use.

You can then use writetable with ‘T1’ (or whatever you wish to name it in your code).

EDIT — (16 Nov 2020 at 20:40)

To have the datetime column in the original format, add the 'Format' name-value pair to the datetime call in the ‘DT’ assignment:

DT = datetime(num2str(M(:,1)), 'InputFormat','yyyyMMdd', 'Format','yyyyMMdd');

The rest of the code is unchanged.

       M1         M2       M3      M4     M5      M6      M7     M8 
    ________    ______    ____    ____    ___    ____    ____    ___
    19790101    7839.4    29.4    17.3    1.6    51.8    13.8    5.2
    19790102    8046.4    30.1    17.5    0.1    45.2    16.2    4.9
    19790103    9018.2    27.6    13.5      0    40.9    14.3    5.2
    19790104    5359.4    21.8    14.4    0.2    61.5       8    4.9
    19790105    8145.9    26.4    13.6    0.7    52.2    11.2    3.8

Best Answer

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