R for loop help to trim based on condition-CodePudding

I am new to R and struggling with for loop: I want to split some strings in a df based on condition my df:

I want to split where begins with "X" to identify I am using - grepl("X.",df1[,1]) to split - str_split_fixed(df1[,1],"X",2)[,2] and not sure how to incorporate that in the loop...

for (i in df1[,1]){
  # if (begins with X) then split
}

so the goal here is to strip "X" from df rows (11 & 12)

Thank you in advance!

CodePudding user response：

R is a vectorized language, so you can just substitute the leading "X" with "" in one line.

df1[,1] <- sub("^X", "", df1[,1])

Using for loop would be very inefficient in this case, but if you insist on that, then

for (i in seq_along(df1[,1])) {
  if (substr(df1[i,1],1,1) == "X")
    df1[i,1] <- substring(df1[i,1],2)
}

Data

df1 <- structure(list(header1 = c("PLAYERID", "YEARID", "STINT", "TEAMID", 
"LGID", "G", "G_BATTING", "AB", "R", "H", "X2B", "X3B", "HR", 
"RBI", "SB", "CS", "BB", "SO", "IBB", "HBP", "SH", "SF", "GIDP", 
"G_OLD")), class = "data.frame", row.names = c(NA, -24L))

CodePudding user response：

for loop

for(i in seq_along(df$header1)){ df$header1[i] <- sub("^X","",df$header1[i]) }
df
      header1
1    DGIGACAE
2  DFGGFAEHBD
3        BIBH
4          EB
5      DHBDFC
6         2BD
7        3GDE
8     DEAEFGE
9           I
10    FFBGDBD

Better vectorized

df$header1 <- sub("^X","",df$header1)
df
      header1
1    DGIGACAE
2  DFGGFAEHBD
3        BIBH
4          EB
5      DHBDFC
6         2BD
7        3GDE
8     DEAEFGE
9           I
10    FFBGDBD

Data

df <- structure(list(header1 = c("DGIGACAE", "DFGGFAEHBD", "BIBH", 
"EB", "DHBDFC", "X2BD", "X3GDE", "DEAEFGE", "I", "FFBGDBD")), row.names = c(NA, 
-10L), class = "data.frame")