cumsum

cumulative sum of array elements

Calling Sequence

y=cumsum(x)

y=cumsum(x,orientation)

y=cumsum(x,outtype)

y=cumsum(x,orientation,outtype)

Arguments

:x an array of reals, complex, booleans, polynomials or rational

fractions.

: :orientation This argument can be

• either a string with possible values “*”, “r”, “c” or “m”
• or a number with positive integer value

: :outtype a string with possible values “native” or “double”. : :y scalar or array :

Description

For an array x, y=cumsum(x) returns in the scalar y the cumulative sum of all the elements of x.

y=cumsum(x,orientation) returns in y the cumulative sum of x along the dimension given by orientation:

• if orientation is equal to 1 or “r” then: or
• if orientation is equal to 2 or “c” then: or
• if orientation is equal to n then:
• y=cumsum(x,”*”) is equivalent to y=cumsum(x)
• y=cumsum(x,”m”) is equivalent to y=cumsum(x,orientation) where orientation is the index of the first dimension of x that is greater than 1. This option is used for Matlab compatibility.

The outtype argument rules the way the summation is done:

• For arrays of floats, of polynomials, of rational fractions, the evaluation is always done using floating points computations. The “double” or “native” options are equivalent.
• For arrays of integers, if outtype=”native” the evaluation is done using integer computations (modulo 2^b, where b is the number of bits used), if outtype=”double” the evaluation is done using floating point computations. The default value is outtype=”native”.
• For arrays of booleans, if outtype=”native” the evaluation is done using boolean computations ( + is replaced by |), if outtype=”double” the evaluation is done using floating point computations (%t values are replaced by 1 and %f values by 0). The default value is outtype=”double”.

Remark

This function applies, with identical rules to sparse matrices and hypermatrices.

Examples

A=[1,2;3,4];
cumsum(A)
cumsum(A,1)

I=`uint8`_([2 95 103;254 9 0])
cumsum(I) //native evaluation
cumsum(I,"double")
cumsum(I,2,"double")

s=`poly`_(0,"s");
P=[s,%i+s;s^2,1];
cumsum(P),
cumsum(P,2)

B=[%t %t %f %f];
cumsum(B) //evaluation in float
cumsum(B,"native") //similar to or(B)

See Also

• sum sum of array elements
• cumprod cumulative product of array elements