I have a simple problem that I wanted to solve using data.table. I was surprised about the following behaviour, as I thought, asignements in base R are always copying: library(data.table) df <- data.frame( t = 1:10, x = "x", y = "y" ) df$z <- df$y # I was assuming this is a full blown… Read More Is `<-` also for data.frames using call by reference sometimes?
I’m trying to find the last element in a data.table by group in a time efficient way. I have a solution that works: library(data.table) Data <- data.table(id = c(rep("a", 2), rep("b",3)), time = c(1:2, 1:3)) Data[, lastobs := max(time), by = id] Data <- Data[time == lastobs] Data[, lastobs := NULL] but the max() by… Read More Find the last element by group in a data.table without max()
I would like to have a dataframe of variables with corresponding unique values (based on a threshold) of the original dataframe. In other words, if a column has less than 5 unique values then it should be added as a row in the new dataframe. For example, based on the following dataframe structure(list(id = c(1,… Read More Dataframe with unique values of some columns
Suppose I have a data table: dt <- data.table(x = c("a,b,b,c,NA","b,b,NA,c","a,b,c,c,c,d")) dt x 1: a,b,b,c,NA 2: b,b,NA,c 3: a,b,c,c,c,d Now for each row I would like to split the x column, extract all unique characters and paste them together so I get: x 1: a,b,c,NA 2: b,NA,c 3: a,b,c,d I have tried this so far… Read More Split string and find unique characters for each row using data.table
I would like to identify and remove duplicates from my dataset. The issue is that I have two different criteria. First, the main criteria that I am using is the most recent time. However, not all duplicates have dates. On the cases dates are missing, I will have to check one by one to see… Read More How to identify and remove duplicates with multiple condition in R
I need to analyse the output of a series of lm() output from a data.table group_by regressions: library(data.table) x <- c(1:5,66:70,101:110) y <- 31:50 g <- c( 1,1,1,1,1,1,1,1,1,1 ,2,2,2,2,2,2,2,2,2,2) dt <- data.table(x,y,g) mod <- dt[ , .(model = .(lm(x~y, .SD))) , by = g] mod has the correct models for each group g. Now I… Read More Recovering lm() results from a data.table groupby models
I have the following df: df<- structure(list(X18.digit.contact.id = c("0034y00002kIZ3rAAG", "0034y00002kIZ3rAAG", "0034y00002kIZ3rAAG", "0034y00002PpX11AAF", "0034y00002PpX11AAF", "0034y00002PpX11AAF", "0034y00002jHjYKAA0", "0034y00002jHjYKAA0", "0034y00002jHjYKAA0"), `Fitness Goal` = c(2L, NA, NA, -1L, NA, NA, NA, 1L, NA), `Nutrition/Hydration Goal` = c(NA, NA, NA, NA, 0L, NA, 2L, NA, NA), `Lifestyle Goal` = c(NA, NA, 2L, NA, NA, 0L, NA, NA, 1L)), class =… Read More Combine multiple rows based on ID column
I have a data.table that has one column, we’ll call it country with repeated values, and another column (survey) that has unique strings for each observation. I want to create a new variable that has the pasted value of all the survey strings for an individual country. I’ve done it with an index and a… Read More concatenate unique strings of variable in data.table by repeated values of another variable in data.table
Say I have 2 df library(data.table) df <- data.table(x = letters[1:2]) df_1 <- data.table(x = letters[3:4]) and I wanted to use set to create a new column in both df (but using an existing column as input) names_df <- c(‘df’, ‘df_1’) for(i in names_df) { set(get(i), j = ‘y’, value = toupper(.$x)) } The above… Read More data.table's set in a loop
I have the following data table in R: library(data.table) dt <- data.table(x = c(NA, NA, NA, NA, NA, NA, NA, "1,2", "NA,3", "NA,NA,NA", "NA,NA,NA,NA", "NA,NA", "NA,4,NA,1", "NA,NA,NA", "NA,NA")) x 1: <NA> 2: <NA> 3: <NA> 4: <NA> 5: <NA> 6: <NA> 7: <NA> 8: 1,2 9: NA,3 10: NA,NA,NA 11: NA,NA,NA,NA 12: NA,NA 13: NA,4,NA,1… Read More Split values of a data.table column and select the lowest number or NA if all are "NA"