submatrix – Tarik Billa

Getting the submatrix with maximum sum?

March 8, 2023 by Tarik

Here’s an explanation to go with the posted code. There are two key tricks to make this work efficiently: (I) Kadane’s algorithm and (II) using prefix sums. You also need to (III) apply the tricks to the matrix. Part I: Kadane’s algorithm Kadane’s algorithm is a way to find a contiguous subsequence with maximum sum. … Read more

Select rows of a matrix that meet a condition

October 25, 2022 by Tarik

This is easier to do if you convert your matrix to a data frame using as.data.frame(). In that case the previous answers (using subset or m$three) will work, otherwise they will not. To perform the operation on a matrix, you can define a column by name: m[m[, “three”] == 11,] Or by number: m[m[,3] == … Read more