string.Rmd

---
title: "Characters and Strings"
author: "Brian S. Yandell"
date: "7/6/2017"
output: html_document
---

```{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)