hhh hhh - 14 days ago 7
R Question

R: `ID : Coercing LHS to a list` in adding an ID column, why?

I have data

N11.1 N22.2 N33.1 N44.1 N21.1 N31.1 N32.1
Sinus 1 0 0 0.0 0 0 12.0
ArrAHB 1 0 0 0.1 0 0 20.9


where I want to add an extra column
ID
with values
Sinus
and
ArrAHB
.

require(lattice)
Sinus<-c(1,0,0,0,0,0,12)
ArrAHB<-c(1,0,0,0.1,0,0,20.9)
Labels<-c("N11.1","N22.2","N33.1","N44.1","N21.1","N31.1","N32.1")
ID<-c("Sinus","Arr/AHB")
data.female<-data.frame(Sinus,ArrAHB,row.names=Labels)
data.female<-t(data.female)

> data.female$ID<-ID

Warning message:
In data.female$ID <- ID : Coercing LHS to a list



Why does the creation of the ID column cause the coercion in the data.frame?


P.s. My goal is to get this data to the form like here for
barchart(N11.1+N22.1+N33.1+N44.1+N21.1+N31.1+N32.1 ~ ID, data=data.female)
which requires a new ID column here, I cannot understand why this ID addition sometimes works and sometimes not. Please explain.

Answer

It's throwing a warning, as the results of transpose t() are a matrix. Matricies don't have accessible column names. You have to coerce the matrix to a data frame before you make the ID assignment, using as.data.frame()

This works.

Sinus<-c(1,0,0,0,0,0,12)
ArrAHB<-c(1,0,0,0.1,0,0,20.9)
Labels<-c("N11.1","N22.2","N33.1","N44.1","N21.1","N31.1","N32.1")
ID<-c("Sinus","Arr/AHB")
data.female<-data.frame(Sinus,ArrAHB,row.names=Labels)
data.female<-as.data.frame(t(data.female))

data.female$ID<-ID

Remember that data frames are defined column-wise and not row-wise. A data frame definition should be by columns.

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