CODEWITHSUNDEEP
rtapply
Vixxen81
Vixxen81

Reputation: 33

Combine tapply to create a matrix

I need to create a matrix with the columns (Swing, Blues, Contra) and Rows (M, F) using Ht data from a data.frame.

I need to create a matrix of NA values and then fill the matrix by row using the outcome from each tapply function.

It needs to look like this:

    Swing    Blues   Contra
M    174.6   186.8   194.5
F    177.7    178    180.4

The 2 tapply functions I have are:

 tapply(dancenewM$Ht,dancenewM$Type,mean)
 tapply(dancenewF$Ht,dancenewF$Type,mean)

sample data: 

  Sex Type   Ht
  F   Swing  177.9 
  F   Swing  177.5 
  F   Contra 179.6 
  F   Contra 181.3 
  F   Blues  179.7 
  F   Blues  176.3 
  M   Swing  172.7  
  M   Swing  176.5 
  M   Contra 194.6
  M   Contra 194.4  
  M   Blues  193.4 
  M   Blues  180.2 "))

Any help with this would be greatly appreciated.

Upvotes: 0

Views: 663

Answers (1)

akrun
akrun

Reputation: 887291

We can use tapply with grouping variables as 'sex' and 'Type' to get the mean of 'Ht'.

with(df1, tapply(Ht, list(Sex = Sex, Type), FUN= mean))

# Sex Blues Contra Swing
#   F 178.0 180.45 177.7
#   M 186.8 194.50 174.6

Or we can use data.table

library(data.table)
dcast(setDT(df1), Sex~Type, value.var='Ht', mean)
#    Sex Blues Contra Swing
# 1:   F 178.0 180.45 177.7
# 2:   M 186.8 194.50 174.6

data

df1 <- structure(list(Sex = structure(c(1L, 1L, 1L, 1L, 1L, 1L, 2L, 
2L, 2L, 2L, 2L, 2L), .Label = c("F", "M"), class = "factor"), 
    Type = structure(c(3L, 3L, 2L, 2L, 1L, 1L, 3L, 3L, 2L, 2L, 
    1L, 1L), .Label = c("Blues", "Contra", "Swing"), class = "factor"), 
    Ht = c(177.9, 177.5, 179.6, 181.3, 179.7, 176.3, 172.7, 176.5, 
    194.6, 194.4, 193.4, 180.2)), .Names = c("Sex", "Type", "Ht"
), class = "data.frame", row.names = c(NA, -12L))

Upvotes: 1

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