Mariano - 9 months ago 47

R Question

I have an lapply function that iterates over a list of elements. For each element, the result is a matrix. Based on the list of elements and the list of matrixes, I would like to return a list of dataframes of the form

`element1, matrix1`

element2, matrix2

...

...

elementn, matrixn

Example:

`e <- list(1,2)`

r <- lapply(e, function(x) matrix(ncol = x, nrow = x))

I would like to get a list with these elements

`(1, matrix(1x1))`

(2, matrix(2x2))

Answer

You can construct data frames in the `lapply`

function, with `I(list(...))`

which can wrap the matrix as one element in the data frame:

```
r <- lapply(e, function(x) data.frame(element = x, mat = I(list(matrix(ncol = x, nrow = x)))))
```

This gives a list of data frames:

```
r
# [[1]]
# element mat
# 1 1 NA
# [[2]]
# element mat
# 1 2 NA, NA, ....
```

You can rbind the result together with `do.call(rbind, ...)`

:

```
do.call(rbind, r)
# element mat
# 1 1 NA
# 2 2 NA, NA, ....
```

Source (Stackoverflow)