Function to Search of Multiple Patterns Using Grep

R's grepl() to find multiple strings exists

Text <- c("instance", "percentage", "n", 
          "instance percentage", "percentage instance")

grepl("instance|percentage", Text)
# TRUE  TRUE FALSE  TRUE  TRUE

grepl("instance.*percentage|percentage.*instance", Text)
# FALSE FALSE FALSE TRUE  TRUE

The latter one works by looking for:

('instance')(any character sequence)('percentage')  
OR  
('percentage')(any character sequence)('instance')

Naturally if you need to find any combination of more than two words, this will get pretty complicated. Then the solution mentioned in the comments would be easier to implement and read.

Another alternative that might be relevant when matching many words is to use positive look-ahead (can be thought of as a 'non-consuming' match). For this you have to activate perl regex.

# create a vector of word combinations
set.seed(1)
words <- c("instance", "percentage", "element",
           "character", "n", "o", "p")
Text2 <- replicate(10, paste(sample(words, 5), collapse=" "))

# grepl with multiple positive look-ahead
longperl <- grepl("(?=.*instance)(?=.*percentage)(?=.*element)(?=.*character)",
  Text2, perl=TRUE)

# this is equivalent to the solution proposed in the comments
longstrd <- grepl("instance", Text2) & 
          grepl("percentage", Text2) & 
             grepl("element", Text2) & 
           grepl("character", Text2)

# they produce identical results
identical(longperl, longstrd)

Furthermore, if you have the patterns stored in a vector you can condense the expressions significantly, giving you

pat <- c("instance", "percentage", "element", "character")

longperl <- grepl(paste0("(?=.*", pat, ")", collapse=""), Text2, perl=TRUE)
longstrd <- rowSums(sapply(pat, grepl, Text2) - 1L) == 0L

---

As asked for in the comments, if you want to match on exact words, i.e. not match on substrings, we can specify word boundaries using \\b. E.g:

tx <- c("cent element", "percentage element", "element cent", "element centimetre")

grepl("(?=.*\\bcent\\b)(?=.*element)", tx, perl=TRUE)
# TRUE FALSE  TRUE FALSE
grepl("element", tx) & grepl("\\bcent\\b", tx)
# TRUE FALSE  TRUE FALSE

Function to search of multiple patterns using grep

I think you can do a recursive function:

search() {
    if [ $# -gt 0 ]; then
        local pat=$1
        shift
        grep "$pat" | search "$@"
    else
         cat
    fi
}

In your script you would call this function and pass the search patterns as arguments. Say that $1 is the file and the rest of the arguments are patterns then you would do

file=$1
shift
cat "$file" | search "$@"

Match two strings in one line with grep

You can use

grep 'string1' filename | grep 'string2'

Or

grep 'string1.*string2\|string2.*string1' filename

Grep multiple patterns and print pattern and its previous lines

You may try this awk:

awk '/^(in|out)put/{print p; print} /^(cell|function|Type)/; {p = $0}' file

cell A
function (A1A2)
Type combinational
(CO)
output
(A1)
input
(A2)
input
cell X
function ((A1+A2)B)
Type combinational
(Z)
output
(A1)
input
(A2)
input
(B)
input

grep multiple patterns Or condition on grouping data

I used dplyr grep to get the desired result.
Below is the code:

library(dplyr) 

pattern <- c("Beach", "sand", "warm")
df <- data.frame(group_id= c(1, 1, 1, 1, 2, 1, 2, 3, 4),
                 words = c("beach", "sand", "trip", "warm","travel", "water","beach","sand", "trees"),
                 ID = c("vacation", "vacation", "vacation", "vacation", "meeting","vacation","meeting","onduty", "hiking"))

x <- df %>%
  group_by(group_id) %>%
  summarise(words = paste(words, collapse = " "))
y <- sapply(pattern, function(d) grep(paste0("\\b",d,"\\b"),x$words , ignore.case = T))
y <- setNames(unlist(y, use.names=F),rep(names(y), lengths(y)))
y <- data.frame(Match_pattern =names(y), group_id=y, row.names=NULL)
y <- y %>%
  group_by(group_id) %>%
  summarise(Match_pattern = paste(Match_pattern, collapse = ", "))

out <- merge(df, y, by = "group_id", all.x = T)
out$N <- ifelse(is.na(out$Match_pattern), 0, 1)

> out
  group_id  words       ID     Match_pattern N
1        1   sand vacation Beach, sand, warm 1
2        1   trip vacation Beach, sand, warm 1
3        1   warm vacation Beach, sand, warm 1
4        1  beach vacation Beach, sand, warm 1
5        1  water vacation Beach, sand, warm 1
6        2  beach  meeting             Beach 1
7        2 travel  meeting             Beach 1
8        3   sand   onduty              sand 1
9        4  trees   hiking              <NA> 0

Use grepl to search either of multiple substrings in a text

You could paste the genres together with an "or" | separator and run that through grepl as a single regular expression.

x <- c("Action", "Adventure", "Animation", ...)
grepl(paste(x, collapse = "|"), my_text)

Here's an example.

x <- c("Action", "Adventure", "Animation")
my_text <- c("This one has Animation.", "This has none.", "Here is Adventure.")
grepl(paste(x, collapse = "|"), my_text)
# [1]  TRUE FALSE  TRUE

---

Related Topics