Cumulative Sum

The cumulative sum, \(\sum_{i=1}^k x_i\) for \(k=1,\ldots,n\). When calling cumsum, matrices are automatically flattened into column-major order before the sum is taken.

cumsum_axis(expr, axis = 2)

# S4 method for class 'Expression'
cumsum(x)

Arguments

axis

(Optional) The dimension across which to apply the function: 1 indicates rows, and 2 indicates columns. The default is 2.

x, expr

An Expression, vector, or matrix.

Examples

val <- cbind(c(1,2), c(3,4))
value(cumsum(Constant(val)))
#>      [,1]
#> [1,]    1
#> [2,]    3
#> [3,]    6
#> [4,]   10
value(cumsum_axis(Constant(val)))
#>      [,1] [,2]
#> [1,]    1    3
#> [2,]    3    7

x <- Variable(2,2)
prob <- Problem(Minimize(cumsum(x)[4]), list(x == val))
result <- solve(prob)
result$value
#> [1] 10
result$getValue(cumsum(x))
#>      [,1]
#> [1,]    1
#> [2,]    3
#> [3,]    6
#> [4,]   10