Creating a matrix from data frame

Question

I have a data frame

df1

with 5 columns

c1

,

c2

,

c3

,

c4

, and

c5

:

df1 <- data.frame(c1 = c(1, 0, 1), c2 = c(0, 0, 1), c3 = c(2, 1, 0), c4 = c(1, 4, 3), c5 = c(1, 0, 0)) 



  #df1

  c1 c2 c3  c4  c5

  1  0  2   1   1

  0  0  1   4   0

  1  1  0   3   0

My desired output is:

  1  3  3   4  5

  3  4  4   4  4

  1  2  4   4  4

Basically, I am creating matrix based on the column number and its value (value is always less than or equal to 5). For example, 2nd row in

df1

has

1

and

4

belongs to column

c3

and

c4

. So, 2nd row in desired matrix would be

3 4 4 4 4

.

I have tried by myself. My code involves several nested control flows and not working well for a large data frame.

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Answer 1

A little apply magic:

t(apply(df, 1, function(x) rep(row(as.matrix(x)), x)))
#     [,1] [,2] [,3] [,4] [,5]
#[1,]    1    3    3    4    5
#[2,]    3    4    4    4    4
#[3,]    1    2    4    4    4

Creating a matrix from data frame

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