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- <font color="#800000"><b>String process</b></font>
Function <code>paste()</code>, <code>nchar()</code>,
<code>strsplit()</code>, <code>substr()</code>, <code>match()</code>, ...
```
a <- paste("string", 9:1, ".txt", sep = "")
nchar(a)
strsplit(a, "\\.")
substr(a, 1, 6) <- "Substr"; a
match("Substr9.txt", a)
```
- <font color="#800000"><b>Regulas expression</b></font>
Function <code>grep()</code>, <code>gsub()</code>, ...
```
a <- paste("string", 9:1, ".txt", sep = "")
grep("([1,3,5-7])", a)
b <- paste("string", 9:1, ".txt", sep = "", collapse = " ")
gsub("([1,3,5-7]).(txt)", "_\\1-\\2", b)
```
- <font color="#800000"><b>Expression and Parse</b></font>
Function <code>expression()</code>, <code>parse()</code>, ...
These are important functions for computing in text and
useful for processing automatically jobs as shown in
"<a href="./batch_more.html">Batch More</a>".
```
a <- 0.05
expression(alpha == 0.05)
(ret <- parse(text = paste("alpha == ", a, sep = "")))
plot(1, 1, main = ret)
text(1, 1.2, ret)
```
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