# Melt: Melting Matrices In mefa4: Multivariate Data Handling with S4 Classes and Sparse Matrices

## Description

The function reverses the side effects of cross tabulation.

## Usage

 `1` ```Melt(x) ```

## Arguments

 `x` A matrix, or sparse matrix object, a list of sparse matrices with identical dimnames, a 'mefa' or 'Mefa' object.

## Value

A data frame with columns corresponding to `rows`, `cols`, possibly `segm` (names of the list if `x` was a list of sparse matrices), and `value`. `value` is numeric, other columns are factors.

## Author(s)

Peter Solymos <solymos@ualberta.ca>

`stack` in utils, and `melt` in mefa package.

## Examples

 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14``` ```xx <- data.frame( sample = paste("Sample", c(1,1,2,2,3,4), sep="."), species = c(paste("Species", c(1,1,1,2,3), sep="."), "zero.pseudo"), count = c(1,2,10,3,4,0), segment = letters[c(6,13,6,13,6,6)], stringsAsFactors = TRUE) xx xx0 <- Xtab(count ~ sample + species, xx) xx1 <- Xtab(count ~ sample + species + segment, xx) (M1 <- Melt(xx0)) Melt(as.matrix(xx0)) (M2 <- Melt(xx1)) stopifnot(identical(Xtab(value ~ rows + cols, M1), xx0)) stopifnot(identical(Xtab(value ~ rows + cols + segm, M2), xx1)) ```

### Example output

```Loading required package: Matrix
mefa4 0.3-7 	 2020-02-28
sample     species count segment
1 Sample.1   Species.1     1       f
2 Sample.1   Species.1     2       m
3 Sample.2   Species.1    10       f
4 Sample.2   Species.2     3       m
5 Sample.3   Species.3     4       f
6 Sample.4 zero.pseudo     0       f
rows      cols value
1 Sample.1 Species.1     3
2 Sample.2 Species.1    10
3 Sample.2 Species.2     3
4 Sample.3 Species.3     4
rows      cols value
1 Sample.1 Species.1     3
2 Sample.2 Species.1    10
3 Sample.2 Species.2     3
4 Sample.3 Species.3     4
rows      cols segm value
1 Sample.1 Species.1    f     1
2 Sample.2 Species.1    f    10
3 Sample.3 Species.3    f     4
4 Sample.1 Species.1    m     2
5 Sample.2 Species.2    m     3
```

mefa4 documentation built on Oct. 7, 2021, 1:06 a.m.