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Dear All, I have a table of 4 columns and many millions rows separated by tab-delimited. I don't have enough memory to read.table in that 1 Gb file. And actually I have 12 text files like that...

Dear ALL, I have a dataframe contains 4 columns and several 10 millions of rows like below! I want to extract out "randomly" say 1 millions of rows, can you tell me how to do that in R using base...

Dear All, I have many 50 objects they are all dataframes. Each dataframe has many rows and four column. I simply want to do an addition of 3rd and 4th column and save the result into 5th column. Since there...

Dear All, I appreciate if you can help me out this. I have a data frame contains many thousand of rows, with some rows that has /// symbol, as shown in in row 2, I want to extract word before ///, such...

Dear All, I have a dataframe like below but with many thousands rows, structure(list(gene_id = structure(1:6, .Label = c("0610005C13Rik", "0610007P14Rik", "0610009B22Rik", "0610009L18Rik", "0610009O20Rik", "0610010B08Rik,OTTMUSG00000016609"), class = "factor"), log2.fold_change. = c(0.0114463, -0.0960262, 0...

So much thanks Rui, the code can be so simple and fast. By the way, ifelse is good for two conditions, in my case, either >0, or <0, I found there's a lot of row with value "Inf", I...

Thanks Henrick. Seems it fits my needs. One my question is the argument, length.out=0.10*n, is it "randomly" taking out 10% ? I found it basically takes every 10th row if I put length.out=0.1*n...