R function used to rename columns of a data frames - r

I have a data frame, say acs10. I need to relabel the columns. To do so, I created another data frame, named as labelName with two columns: The first column contains the old column names, and the second column contains names I want to use, like the table below:
column_1
column_2
oldLabel1
newLabel1
oldLabel2
newLabel2
Then, I wrote a for loop to change the column names:
for (i in seq_len(nrow(labelName))){
names(acs10)[names(acs10) == labelName[i,1]] <- labelName[i,2]}
, and it works.
However, when I tried to put the for loop into a function, because I need to rename column names for other data frames as well, the function failed. The function I wrote looks like below:
renameDF <- function(dataF,varName){
for (i in seq_len(nrow(varName))){
names(dataF)[names(dataF) == varName[i,1]] <- varName[i,2]
print(varName[i,1])
print(varName[i,2])
print(names(dataF))
}
}
renameDF(acs10, labelName)
where dataF is the data frame whose names I need to change, and varName is another data frame where old variable names and new variable names are paired. I used print(names(dataF)) to debug, and the print out suggests that the function works. However, the calling the function does not actually change the column names. I suspect it has something to do with the scope, but I want to know how to make it works.

In your function you need to return the changed dataframe.
renameDF <- function(dataF,varName){
for (i in seq_len(nrow(varName))){
names(dataF)[names(dataF) == varName[i,1]] <- varName[i,2]
}
return(dataF)
}
You can also simplify this and avoid for loop by using match :
renameDF <- function(dataF,varName){
names(dataF) <- varName[[2]][match(names(dataF), varName[[1]])]
return(dataF)
}

This should do the whole thing in one line.
colnames(acs10)[colnames(acs10) %in% labelName$column_1] <- labelName$column_2[match(colnames(acs10)[colnames(acs10) %in% labelName$column_1], labelName$column_1)]

This will work if the column name isn't in the data dictionary, but it's a bit more convoluted:
library(tibble)
df <- tribble(~column_1,~column_2,
"oldLabel1", "newLabel1",
"oldLabel2", "newLabel2")
d <- tibble(oldLabel1 = NA, oldLabel2 = NA, oldLabel3 = NA)
fun <- function(dat, dict) {
names(dat) <- sapply(names(dat), function(x) ifelse(x %in% dict$column_1, dict[dict$column_1 == x,]$column_2, x))
dat
}
fun(d, df)

You can create a function containing just on line of code.
renameDF <- function(df, varName){
setNames(df,varName[[2]][pmatch(names(df),varName[[1]])])
}

Related

Removing a row by string-matching in R regardless of whether it exists or not

I am trying to remove a row in a dataframe based on string matching. I'm using:
data <- data[- grep("my_string", data$field1),]
When there's an actual row with the value "my_string" in data$field1 this works as expected and it drops that row. However, if there is no string "my_string", it creates an empty dataframe. How to I do write this so that it allows for the possibility of the string to not exist, and still keeps my data frame intact?
It may be better to use grepl and negate with !
data[!grepl("my_string", data$field1),]
Or another option is setdiff on grep
data[setdiff(seq_len(nrow(data)), grep("my_string", data$field1)),]
You can use a plain if statement.
df <- data.frame(fieled = c("my_string", "my_string_not", "something", "something_else"),
numbers = 1:4)
result <- grep("gabriel", df$fieled)
if (length(result))
{
df <- df[- result, ]
}
df
result <- grep("my_string", df$fieled)
if (length(result))
{
df <- df[- result, ]
}
df

Refer to a variable by pasting strings then make changes and see them refrelcted in the original variable

my_mtcars_1 <- mtcars
my_mtcars_2 <- mtcars
my_mtcars_3 <- mtcars
for(i in 1:3) {get(paste0('my_mtcars_', i))$blah <- 1}
Error in get(paste0("my_mtcars_", i))$blah <- 1 :
target of assignment expands to non-language object
I would like each of my 3 data frames to have a new field called blah that has a value of 1.
How can I iterate over a range of numbers in a loop and refer to DFs by name by pasting the variable name into a string and then edit the df in this way?
These three options all assume you want to modify them and keep them in the environment.
So, if it must be a dataframes (in your environment & in a loop) you could do something like this:
for(i in 1:3) {
obj_name = paste0('my_mtcars_', i)
obj = get(obj_name)
obj$blah = 1
assign(obj_name, obj, envir = .GlobalEnv) # Send back to global environment
}
I agree with #Duck that a list is a better format (and preferred to the above loop). So, if you use a list and need it in your environment, use what Duck suggested with list2env() and send everything back to the .GlobalEnv. I.e. (in one ugly line),
list2env(lapply(mget(ls(pattern = "my_mtcars_")), function(x) {x[["blah"]] = 1; x}), .GlobalEnv)
Or, if you are amenable to working with data.table, you could use the set() function to add columns:
library(data.table)
# assuming my_mtcars_* is already a data.table
for(i in 1:3) {
set(get(paste0('my_mtcars_', i)), NULL, "blah", 1)
}
As suggestion, it is better if you manage data inside a list and use lapply() instead of loop:
#List
List <- list(my_mtcars_1 = mtcars,
my_mtcars_2 = mtcars,
my_mtcars_3 = mtcars)
#Variable
List2 <- lapply(List,function(x) {x$bla <- 1;return(x)})
And it is easy to store your data using a code like this:
#List
List <- mget(ls(pattern = 'my_mt'))
So no need of defining each dataset individually.
We can use tidyverse
library(dplyr)
library(purrr)
map(mget(ls(pattern = '^my_mtcars_\\d+$')), ~ .x %>%
mutate(blah = 1)) %>%
list2env(.GlobalEnv)

R: How can I append multiple rows to a data.frame during a loop?

I discovered that it seems that I can not add rows to a data.frame in place.
The following code is a minimal example which should append a new row to the data.frame every iteration, but it does not append any.
Please note, in reality I have a complex for-loop with a lot of different if-statements and depending on them I want to append new different data to different data frames.
df <- data.frame(value=numeric())
appendRows <- function(n_rows) {
for(i in 1:n_rows) {
print(i)
df <- rbind(df, setNames(i,names(df)))
}
}
appendRows(10) #Does not append any row, whereas "df <- rbind(df, setNames(1,names(df)))" in a single call appends one row.
How can rows be added to a data.frame in place?
Thanks :-)
Don't forget to return your object:
df <- data.frame(value=numeric())
appendRows <- function(n_rows) {
for(i in 1:n_rows) {
print(i)
df <- rbind(df, setNames(i,names(df)))
}
return(df)
}
appendRows(10)
To modify df you have to store it:
df <- appendRows(10)

Converting list of Characters to Named num in R

I want to create a dataframe with 3 columns.
#First column
name_list = c("ABC_D1", "ABC_D2", "ABC_D3",
"ABC_E1", "ABC_E2", "ABC_E3",
"ABC_F1", "ABC_F2", "ABC_F3")
df1 = data.frame(C1 = name_list)
These names in column 1 are a bunch of named results of the cor.test function. The second column should consist of the correlation coefficents I get by writing ABC_D1$estimate, ABC_D2$estimate.
My problem is now that I dont want to add the $estimate manually to every single name of the first column. I tried this:
df1$C2 = paste0(df1$C1, '$estimate')
But this doesnt work, it only gives me this back:
"ABC_D1$estimate", "ABC_D2$estimate", "ABC_D3$estimate",
"ABC_E1$estimate", "ABC_E2$estimate", "ABC_E3$estimate",
"ABC_F1$estimate", "ABC_F2$estimate", "ABC_F3$estimate")
class(df1$C2)
[1] "character
How can I get the numeric result for ABC_D1$estimate in my dataframe? How can I convert these characters into Named num? The 3rd column should constist of the results of $p.value.
As pointed out by #DSGym there are several problems, including the it is not very convenient to have a list of character names, and it would be better to have a list of object instead.
Anyway, I think you can get where you want using:
estimates <- lapply(name_list, function(dat) {
dat_l <- get(dat)
dat_l[["estimate"]]
}
)
cbind(name_list, estimates)
This is not really advisable but given those premises...
Ok I think now i know what you need.
eval(parse(text = paste0("ABC_D1", '$estimate')))
You connect the two strings and use the functions parse and eval the get your results.
This it how to do it for your whole data.frame:
name_list = c("ABC_D1", "ABC_D2", "ABC_D3",
"ABC_E1", "ABC_E2", "ABC_E3",
"ABC_F1", "ABC_F2", "ABC_F3")
df1 = data.frame(C1 = name_list)
df1$C2 <- map_dbl(paste0(df1$C1, '$estimate'), function(x) eval(parse(text = x)))

Subset variables in data frame based on column type

I need to subset data frame based on column type - for example from data frame with 100 columns I need to keep only those column with type factor or integer. I've written a short function to do this, but is there any simpler solution or some built-in function or package on CRAN?
My current solution to get variable names with requested types:
varlist <- function(df=NULL, vartypes=NULL) {
type_function <- c("is.factor","is.integer","is.numeric","is.character","is.double","is.logical")
names(type_function) <- c("factor","integer","numeric","character","double","logical")
names(df)[as.logical(sapply(lapply(names(df), function(y) sapply(type_function[names(type_function) %in% vartypes], function(x) do.call(x,list(df[[y]])))),sum))]
}
The function varlist works as follows:
For every requested type and for every column in data frame call "is.TYPE" function
Sum tests for every variable (boolean is casted to integer automatically)
Cast result to logical vector
subset names in data frame
And some data to test it:
df <- read.table(file="http://archive.ics.uci.edu/ml/machine-learning-databases/statlog/german/german.data", sep=" ", header=FALSE, stringsAsFactors=TRUE)
names(df) <- c('ca_status','duration','credit_history','purpose','credit_amount','savings', 'present_employment_since','installment_rate_income','status_sex','other_debtors','present_residence_since','property','age','other_installment','housing','existing_credits', 'job','liable_maintenance_people','telephone','foreign_worker','gb')
df$gb <- ifelse(df$gb == 2, FALSE, TRUE)
df$property <- as.character(df$property)
varlist(df, c("integer","logical"))
I'm asking because my code looks really cryptic and hard to understand (even for me and I've finished the function 10 minutes ago).
Just do the following:
df[,sapply(df,is.factor) | sapply(df,is.integer)]
subset_colclasses <- function(DF, colclasses="numeric") {
DF[,sapply(DF, function(vec, test) class(vec) %in% test, test=colclasses)]
}
str(subset_colclasses(df, c("factor", "integer")))

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