```{r setup, include=FALSE} knitr::opts_chunk$set(echo = TRUE) ``` - [Jenny Bryan's Data analysis 2: vectors](http://stat545.com/topics.html) (scroll down) - [regular expressions](regex.Rmd) - [stringr](http://stringr.tidyverse.org/) - [tidytext: Julia Silge & David Robinson](http://tidytextminig.com) | [github](https://github.com/juliasilge/tidytext) | [blog](http://juliasilge.com/blog/Tidy-Text-Mining/) Sometimes one may want to change names of columns in a table. Here is what might seem like a logical approach, but it is in fact difficult to read, awkward and repetitive, and slow. ``` new_names=list() l=1 for(n in colnames(x)){ ifelse((l<10), (colnames(x)[l]=c(paste0('Otu000',c(l)))), (colnames(x)[l]=c(paste0('Otu00',c(l))))) new_names=append(new_names, colnames(x)[l]) l=l+1 } ``` Here is an improved version: ``` new_names <- paste0("Otu", stringr::str_pad(seq_along(colnames(x)), 4, pad="0")) ``` It might be helpful to work up the full example, showing original code and improved version. - [Andrew Steinberger code](https://github.com/asteinberger9/seq_scripts)