Is it possible to include two functions within a single tapply or aggregate statement? Below I use two tapply statements and two aggregate statements: one for mean and one for SD. I would prefer t...

I would like to draw a plot with percentage labels per x-axis group. This works fine without empty groups: # library library(ggplot2) library(reshape2) # example data from reshape2 str(tips) #>...

I have a dataframe similar to this one ID <- c(1,1,1,1,1,2,2,2,2,2,3,3,3,3,3) p1 <- c(21000, 23400, 26800, 2345, 23464, 34563, 456433, 56543, 34543,3524, 353, 3432, 4542, 6343, 4534 ) ...

I have two data frames, df1 with reference data and df2 with new data. For each row in df2, I need to find the best (and the second best) matching row to df1 in terms of hamming distance. I used e...

I would like to apply grep() in R, but I am not really good in lapply(). I understand that lapply is able to take a list, apply function to each members and output a list. For instance, let x be a ...

I have the following df: group = rep(seq(1,3),30) variable = runif(90, 5.0, 7.5) df = data.frame(group,variable) I need to i) Define quantile by groups, ii) Assign each person to her quantile wi...

How do I combine the tapply command with 'not in' logic? Objective: Obtain the median sepal length for each species. tapply(iris$Sepal.Length, iris$Species, median) Constraint: Remove entries ...

There seems to be general agreement that the l in "lapply" stands for list, the s in "sapply" stands for simplify and the r in "rapply" stands for recursively. But I could not find anything on the ...

I´d like to calculate mean and sd from a dataframe with one column for the parameter and one column for a group identifier. How can I calculate them when using tapply? I could use sd(v1, group, na....

I have a matrix, data.mat, that looks like: A B C D E 45 43 45 65 23 12 45 56 NA NA 13 4 34 12 NA I am trying to turn this into a list of lists, where each row is one list within a bigger li...

Say I have data that looks like date, user, items_bought, event_number 2013-01-01, x, 2, 1 2013-01-02, x, 1, 2 2013-01-03, x, 0, 3 2013-01-04, x, 0, 4 2013-01-04, x, 1, 5 2013-01-04, x, 2, 6 2013-...

I can't wrap my mind around the ave function. I read the help and searched the net but I still cannot understand what it does. I understand it applies some function on a subset of observation but n...

I have a dataset that contains the feeding data of 3 animals, consisting of the animals' tag ids (1,2,3), the type (A,B) and amount (kg) of feed given at each 'meal': Animal FeedType Amount(kg) A...

I am trying to find the summary statistics for different factor levels. data.frame(apply(final_data[Company=="BPO",c(66:84)],2,summary)) Now I have different values for company - i can repeat ...

I wanted to sum individual columns by group and my first thought was to use tapply. However, I cannot get tapply to work. Can tapply be used to sum multiple columns? If not, why not? I have search...

I have the following data: a <- c(1,1,1,1,2,2,2,2) b <- c(2,4,6,8,2,3,4,1) c <- factor(c("A","B","A","B","A","B","A","B")) df <- data.frame( sp=a, length=b, method=c) I can use th...

Does the by function make a list that grows one element at a time? I need to process a data frame with about 4M observations grouped by a factor column. The situation is similar to the example bel...

My question is: I have a data frame with some factor variables. I now want to assign a new vector to this data frame, which creates an index for each subset of those factor variables. data <-d...

I've learned R by toying, and I'm starting to think that I'm abusing the tapply function. Are there better ways to do some of the following actions? Granted, they work, but as they get more complex...