What R object can hold variables so I can iterate over the object?





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This seems simple, but I'm spinning my wheels.



I have 80 character variables. I want to 1) view the unique values in each variable, 2) view the number of unique values, and 3) convert some or all variables to factors.



I can do this one-by-one by explicitly naming the columns:



df$var1 # "val2" "val2" "val1" "val2" ... 

unique(df$var1) # "val1" "val2" "val3" 

length(unique(df$var1)) # 3 

df$var1 = as.factor(df$var1)


... although this produces an error:



levels(df@var1)

# Error in levels(df@var1) : 

# trying to get slot "var1" from an object (class "tbl_df") 

# that is not an S4 object


But when I create a list of the character variables and try the same as above it doesn't work.



# create list of char vars

char_vars_names <- names(df[, sapply(df, class) == 'character'])

char_vars_names

#[1] "var1" "var2" "var3" ...



df$char_vars_names[1]  # NULL

# Warning message: Unknown or uninitialised column: 'char_vars_names'.



unique(df$char_vars_names[1])  # NULL

length(unique(df$char_vars_names[1]))  # 0


Once I get the above working I figure I can iterate over the list with a for loop:



for (i in range(length(char_vars_names))) {

    # code


}



What is it about the char_vars_names object or elsewhere in my code that makes this not work?



In case it's helpful, here's my imports and data ingestion prior to the above code:



library(car) 

library(lattice)

library(tidyverse)

library(ISLR)

library(Lahman) 

library(mdsr)



file = "file.csv"

df <- read_csv(

    file=file,

    col_names = TRUE,  

    skip = 3,

    na = c("", "NA"))





r for-loop variables







share|improve this question


















  • 3





    Try df[[char_vars_names]][1]. The $ notation can't take advantage of variable substitution, but the double brackets can.

    – jdobres
    Nov 23 '18 at 21:06






  • 3





    Also your use of range will not work (I'm guessing you're coming from Python). for (i in char_vars_names) might be what you're after.

    – jdobres
    Nov 23 '18 at 21:07













  • I get an error when I use the double bracket below, but maybe I didn't follow your suggestion correctly: char_vars_names # [1] "var1" "var2" ... char_vars_names[1] # "var1" # Works/works/doesn't work: df$var1 # "val2" "val2" "val1" ... df[char_vars_names][1] # "val2" "val2" "val1" ... df[[char_vars_names]][1] # Error in .subset2(x, i) : recursive indexing failed at level 2

    – Karl Baker
    Nov 24 '18 at 0:01











  • Thanks for the tip on the for loop. That is exactly what I'll need as soon as I can get the rest of the code to work!

    – Karl Baker
    Nov 24 '18 at 0:10


















0















This seems simple, but I'm spinning my wheels.



I have 80 character variables. I want to 1) view the unique values in each variable, 2) view the number of unique values, and 3) convert some or all variables to factors.



I can do this one-by-one by explicitly naming the columns:



df$var1 # "val2" "val2" "val1" "val2" ... 

unique(df$var1) # "val1" "val2" "val3" 

length(unique(df$var1)) # 3 

df$var1 = as.factor(df$var1)


... although this produces an error:



levels(df@var1)

# Error in levels(df@var1) : 

# trying to get slot "var1" from an object (class "tbl_df") 

# that is not an S4 object


But when I create a list of the character variables and try the same as above it doesn't work.



# create list of char vars

char_vars_names <- names(df[, sapply(df, class) == 'character'])

char_vars_names

#[1] "var1" "var2" "var3" ...



df$char_vars_names[1]  # NULL

# Warning message: Unknown or uninitialised column: 'char_vars_names'.



unique(df$char_vars_names[1])  # NULL

length(unique(df$char_vars_names[1]))  # 0


Once I get the above working I figure I can iterate over the list with a for loop:



for (i in range(length(char_vars_names))) {

    # code


}



What is it about the char_vars_names object or elsewhere in my code that makes this not work?



In case it's helpful, here's my imports and data ingestion prior to the above code:



library(car) 

library(lattice)

library(tidyverse)

library(ISLR)

library(Lahman) 

library(mdsr)



file = "file.csv"

df <- read_csv(

    file=file,

    col_names = TRUE,  

    skip = 3,

    na = c("", "NA"))





r for-loop variables







share|improve this question


















  • 3





    Try df[[char_vars_names]][1]. The $ notation can't take advantage of variable substitution, but the double brackets can.

    – jdobres
    Nov 23 '18 at 21:06






  • 3





    Also your use of range will not work (I'm guessing you're coming from Python). for (i in char_vars_names) might be what you're after.

    – jdobres
    Nov 23 '18 at 21:07













  • I get an error when I use the double bracket below, but maybe I didn't follow your suggestion correctly: char_vars_names # [1] "var1" "var2" ... char_vars_names[1] # "var1" # Works/works/doesn't work: df$var1 # "val2" "val2" "val1" ... df[char_vars_names][1] # "val2" "val2" "val1" ... df[[char_vars_names]][1] # Error in .subset2(x, i) : recursive indexing failed at level 2

    – Karl Baker
    Nov 24 '18 at 0:01











  • Thanks for the tip on the for loop. That is exactly what I'll need as soon as I can get the rest of the code to work!

    – Karl Baker
    Nov 24 '18 at 0:10














0












0








0








This seems simple, but I'm spinning my wheels.



I have 80 character variables. I want to 1) view the unique values in each variable, 2) view the number of unique values, and 3) convert some or all variables to factors.



I can do this one-by-one by explicitly naming the columns:



df$var1 # "val2" "val2" "val1" "val2" ... 

unique(df$var1) # "val1" "val2" "val3" 

length(unique(df$var1)) # 3 

df$var1 = as.factor(df$var1)


... although this produces an error:



levels(df@var1)

# Error in levels(df@var1) : 

# trying to get slot "var1" from an object (class "tbl_df") 

# that is not an S4 object


But when I create a list of the character variables and try the same as above it doesn't work.



# create list of char vars

char_vars_names <- names(df[, sapply(df, class) == 'character'])

char_vars_names

#[1] "var1" "var2" "var3" ...



df$char_vars_names[1]  # NULL

# Warning message: Unknown or uninitialised column: 'char_vars_names'.



unique(df$char_vars_names[1])  # NULL

length(unique(df$char_vars_names[1]))  # 0


Once I get the above working I figure I can iterate over the list with a for loop:



for (i in range(length(char_vars_names))) {

    # code


}



What is it about the char_vars_names object or elsewhere in my code that makes this not work?



In case it's helpful, here's my imports and data ingestion prior to the above code:



library(car) 

library(lattice)

library(tidyverse)

library(ISLR)

library(Lahman) 

library(mdsr)



file = "file.csv"

df <- read_csv(

    file=file,

    col_names = TRUE,  

    skip = 3,

    na = c("", "NA"))





r for-loop variables







share|improve this question














This seems simple, but I'm spinning my wheels.



I have 80 character variables. I want to 1) view the unique values in each variable, 2) view the number of unique values, and 3) convert some or all variables to factors.



I can do this one-by-one by explicitly naming the columns:



df$var1 # "val2" "val2" "val1" "val2" ... 

unique(df$var1) # "val1" "val2" "val3" 

length(unique(df$var1)) # 3 

df$var1 = as.factor(df$var1)


... although this produces an error:



levels(df@var1)

# Error in levels(df@var1) : 

# trying to get slot "var1" from an object (class "tbl_df") 

# that is not an S4 object


But when I create a list of the character variables and try the same as above it doesn't work.



# create list of char vars

char_vars_names <- names(df[, sapply(df, class) == 'character'])

char_vars_names

#[1] "var1" "var2" "var3" ...



df$char_vars_names[1]  # NULL

# Warning message: Unknown or uninitialised column: 'char_vars_names'.



unique(df$char_vars_names[1])  # NULL

length(unique(df$char_vars_names[1]))  # 0


Once I get the above working I figure I can iterate over the list with a for loop:



for (i in range(length(char_vars_names))) {

    # code


}



What is it about the char_vars_names object or elsewhere in my code that makes this not work?



In case it's helpful, here's my imports and data ingestion prior to the above code:



library(car) 

library(lattice)

library(tidyverse)

library(ISLR)

library(Lahman) 

library(mdsr)



file = "file.csv"

df <- read_csv(

    file=file,

    col_names = TRUE,  

    skip = 3,

    na = c("", "NA"))





r for-loop variables




r for-loop variables






share|improve this question













share|improve this question











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share|improve this question










asked Nov 23 '18 at 20:54









Karl BakerKarl Baker

366115




366115








  • 3





    Try df[[char_vars_names]][1]. The $ notation can't take advantage of variable substitution, but the double brackets can.

    – jdobres
    Nov 23 '18 at 21:06






  • 3





    Also your use of range will not work (I'm guessing you're coming from Python). for (i in char_vars_names) might be what you're after.

    – jdobres
    Nov 23 '18 at 21:07













  • I get an error when I use the double bracket below, but maybe I didn't follow your suggestion correctly: char_vars_names # [1] "var1" "var2" ... char_vars_names[1] # "var1" # Works/works/doesn't work: df$var1 # "val2" "val2" "val1" ... df[char_vars_names][1] # "val2" "val2" "val1" ... df[[char_vars_names]][1] # Error in .subset2(x, i) : recursive indexing failed at level 2

    – Karl Baker
    Nov 24 '18 at 0:01











  • Thanks for the tip on the for loop. That is exactly what I'll need as soon as I can get the rest of the code to work!

    – Karl Baker
    Nov 24 '18 at 0:10














  • 3





    Try df[[char_vars_names]][1]. The $ notation can't take advantage of variable substitution, but the double brackets can.

    – jdobres
    Nov 23 '18 at 21:06






  • 3





    Also your use of range will not work (I'm guessing you're coming from Python). for (i in char_vars_names) might be what you're after.

    – jdobres
    Nov 23 '18 at 21:07













  • I get an error when I use the double bracket below, but maybe I didn't follow your suggestion correctly: char_vars_names # [1] "var1" "var2" ... char_vars_names[1] # "var1" # Works/works/doesn't work: df$var1 # "val2" "val2" "val1" ... df[char_vars_names][1] # "val2" "val2" "val1" ... df[[char_vars_names]][1] # Error in .subset2(x, i) : recursive indexing failed at level 2

    – Karl Baker
    Nov 24 '18 at 0:01











  • Thanks for the tip on the for loop. That is exactly what I'll need as soon as I can get the rest of the code to work!

    – Karl Baker
    Nov 24 '18 at 0:10








3




3





Try df[[char_vars_names]][1]. The $ notation can't take advantage of variable substitution, but the double brackets can.

– jdobres
Nov 23 '18 at 21:06





Try df[[char_vars_names]][1]. The $ notation can't take advantage of variable substitution, but the double brackets can.

– jdobres
Nov 23 '18 at 21:06




3




3





Also your use of range will not work (I'm guessing you're coming from Python). for (i in char_vars_names) might be what you're after.

– jdobres
Nov 23 '18 at 21:07







Also your use of range will not work (I'm guessing you're coming from Python). for (i in char_vars_names) might be what you're after.

– jdobres
Nov 23 '18 at 21:07















I get an error when I use the double bracket below, but maybe I didn't follow your suggestion correctly: char_vars_names # [1] "var1" "var2" ... char_vars_names[1] # "var1" # Works/works/doesn't work: df$var1 # "val2" "val2" "val1" ... df[char_vars_names][1] # "val2" "val2" "val1" ... df[[char_vars_names]][1] # Error in .subset2(x, i) : recursive indexing failed at level 2

– Karl Baker
Nov 24 '18 at 0:01





I get an error when I use the double bracket below, but maybe I didn't follow your suggestion correctly: char_vars_names # [1] "var1" "var2" ... char_vars_names[1] # "var1" # Works/works/doesn't work: df$var1 # "val2" "val2" "val1" ... df[char_vars_names][1] # "val2" "val2" "val1" ... df[[char_vars_names]][1] # Error in .subset2(x, i) : recursive indexing failed at level 2

– Karl Baker
Nov 24 '18 at 0:01













Thanks for the tip on the for loop. That is exactly what I'll need as soon as I can get the rest of the code to work!

– Karl Baker
Nov 24 '18 at 0:10





Thanks for the tip on the for loop. That is exactly what I'll need as soon as I can get the rest of the code to work!

– Karl Baker
Nov 24 '18 at 0:10












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