Extract rows of data frame with specific conditions
I have a data frame, two variables V1
and V2
, with 9 lines of data.
Original Data Frame:
Var1 Var2
sigma1 11 1
alpha1 12 5
pi1 13 3
sigma2 14 4
alpha2 21 9
pi2 34 6
sigma3 55 12
alpha3 18 9
pi3 19 10
I want to separate all the alpha, sigma and pi observations. And make each one a new dataframe.
Ideal format afterwards:
Data Frame 1:
sigma1 11 1
sigma2 14 4
sigma3 55 12
Data Frame 2:
alpha1 12 5
alpha2 21 9
alpha3 18 9
Data Frame 3:
pi1 13 3
pi2 34 6
pi3 19 10
I want to separate all the alpha, sigma and pi observations. And make each one a new dataframe.
+3
source to share
3 answers
We can use eval(parse())
to create dynamic variables, try this example:
#dummy data
df <- read.table(text="Var1 Var2
sigma1 11 1
alpha1 12 5
pi1 13 3
sigma2 14 4
alpha2 21 9
pi2 34 6
sigma3 55 12
alpha3 18 9
pi3 19 10")
#get unique rownames
myNames <- unique(gsub(".$", "", rownames(df)))
myNames
#[1] "sigma" "alpha" "pi"
#split to 3 data.frames
for(i in myNames)
eval(parse(text=paste0("df_",i," <- df[ grepl('",i,"',rownames(df)),]")))
#check output
ls()
# [1] "df" "df_alpha" "df_pi" "df_sigma" "i" "myNames"
df_alpha
# Var1 Var2
# alpha1 12 5
# alpha2 21 9
# alpha3 18 9
EDIT: As suggested by @NealFultz to improve code readability, we can use assignment:
for(i in myNames)
assign(paste0("df_",i),df[ grepl(i,rownames(df)),])
+2
source to share
I would make a grouping variable from the first letter and use it with split:
df <- read.table(header=T, text='
group Var1 Var2
sigma1 11 1
alpha1 12 5
pi1 13 3
sigma2 14 4
alpha2 21 9
pi2 34 6
sigma3 55 12
alpha3 18 9
pi3 19 10
')
split(df, substr(df$group,0,1))
give this:
> split(df, substr(df$group,0,1))
$a
group Var1 Var2
2 alpha1 12 5
5 alpha2 21 9
8 alpha3 18 9
$p
group Var1 Var2
3 pi1 13 3
6 pi2 34 6
9 pi3 19 10
$s
group Var1 Var2
1 sigma1 11 1
4 sigma2 14 4
7 sigma3 55 12
+2
source to share