CODEWITHSUNDEEP
rmatrix
inmierp
inmierp

Reputation: 45

Create a matrix with another matrix in R

So, I have a dataset (usage) that is like the following, in R:

Item    Bike    Usage
item1   bike1   1
item2   bike1   2
item1   bike2   1
item3   bike2   2

And I wanted to convert on a matrix with the usage. I created a matrix where my header is the bikes (bike 1, bike2), and the row names is (item 1, item 2, item 3), and filled with NA and now I want to fill it the usage, such as:

bike1  bike2
item 1 1      1
item 2 1      0
item 3 0      1

I created the following loop: 

for (i in 1:nrow(usage)) {
  item<-usage[i,1]
  bike<-usage[i,2]
  matriz[item,bike]<-usage[i,3]

matriz[is.na(matriz)]<-0

}

But I get this error:

Error in `[<-`(`*tmp*`, item, bike, value = list(Usage = 6)) : 
  invalid subscript type 'list'

Upvotes: 1

Views: 54

Answers (3)

akrun
akrun

Reputation: 886948

One option is acast from reshape2

library(reshape2)
acast(df,  Item ~ Bike, fill = 0)
#       bike1 bike2
#item1     1     1
#item2     2     0
#item3     0     2

data

df <- structure(list(Item = c("item1", "item2", "item1", "item3"), 
    Bike = c("bike1", "bike1", "bike2", "bike2"), Usage = c(1L, 
    2L, 1L, 2L)), class = "data.frame", row.names = c(NA, -4L
))

Upvotes: 0

ThomasIsCoding
ThomasIsCoding

Reputation: 101064

Maybe you can try xtabs if you need table

res_tb <- xtabs(Usage~.,df)

such that

> res_tb
       Bike
Item    bike1 bike2
  item1     1     1
  item2     2     0
  item3     0     2

DATA

df <- structure(list(Item = c("item1", "item2", "item1", "item3"), 
    Bike = c("bike1", "bike1", "bike2", "bike2"), Usage = c(1L, 
    2L, 1L, 2L)), class = "data.frame", row.names = c(NA, -4L
))

Upvotes: 0

r2evans
r2evans

Reputation: 160407

library(tidyr)
pivot_wider(dat, "Item", names_from="Bike",
            values_from="Usage", values_fill=list(Usage=0))
# # A tibble: 3 x 3
#   Item  bike1 bike2
#   <chr> <int> <int>
# 1 item1     1     1
# 2 item2     2     0
# 3 item3     0     2

Data:

dat <- structure(list(Item = c("item1", "item2", "item1", "item3"), 
    Bike = c("bike1", "bike1", "bike2", "bike2"), Usage = c(1L, 
    2L, 1L, 2L)), class = "data.frame", row.names = c(NA, -4L
))

Upvotes: 1

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