sum!(r, A)

Sum elements of A over the singleton dimensions of r, and write results to r.


  1. Sum elements of a vector and store the result in another vector:

    julia> A = [1, 2, 3, 4, 5];
    julia> r = similar(A);
    julia> sum!(r, A)
    5-element Array{Int64,1}:

    This example computes the cumulative sum of the elements in vector A and stores the result in vector r.

  2. Sum elements of a matrix along the rows:

    julia> A = [1 2 3; 4 5 6; 7 8 9];
    julia> r = similar(A, 1, size(A, 2));
    julia> sum!(r, A)
    1×3 Array{Int64,2}:
    12  15  18

    It calculates the sum of each row of matrix A and stores the resulting row vector in r.

  3. Compute column-wise sum of a matrix:
    julia> A = [1 2 3; 4 5 6; 7 8 9];
    julia> r = similar(A, size(A, 1), 1);
    julia> sum!(r, A)
    3×1 Array{Int64,2}:

    This example computes the sum of each column of matrix A and stores the resulting column vector in r.

Common mistake example:

julia> A = [1 2 3; 4 5 6; 7 8 9];
julia> r = [0, 0, 0];
julia> sum!(r, A)
ERROR: DimensionMismatch("output array has wrong dimensions for sum")

In this case, the output array r has the wrong dimensions to store the result of the sum operation. It's important to ensure that the size and dimensions of r match the expected result based on the dimensions of A.

See Also

abs2, beta, binomial, ceil, cell, cross, ctranspose, ctranspose!, cummin, cumprod, cumprod!, cumsum, cumsum!, cumsum_kbn, div, divrem, eigfact, eigfact!, eigmin, eps, erf, erfc, erfcinv, erfcx, erfi, erfinv, exp, exp10, exp2, expm1, exponent, factor, factorial, factorize, floor, gcd, invmod, log, log10, log1p, log2, logspace, max, min, mod, mod1, modf, next, nextpow, nextprod, num, primes, primesmask, prod, realmin, sqrt, sum!, sumabs, sumabs!, sumabs2, sumabs2!,

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