R - .csv file - extract variables [closed] - r

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I pulled in a large .csv file with columns such as "paid" and "description"
I am trying to figure out how to only pull the "paid" column when the "description" is Bronchitis or some other illness that is in the column.
This would be like doing a pivot table in Excel and filtering only on a certain Description and receiving all of the individual paid rows.
Paid Description val
$500 Bronchitis 1.5
$3,250 'Complication of Pregnancy/Childbirth' 2.2
$5,400 Burns 3.3
$20.50 Bronchitis 4.4
$24 Ashtma 1.2

Answer 1

If your data is
paid <- c(300,200,150)
desc <- c("bronchitis","headache","broken.leg")
df <- data.frame(paid, desc)
Try
df[desc=="bronchitis",c("paid")]
# the argument ahead of the comma filters the row,
# the argument after the comma refers to the column
# > df[desc=="bronchitis",c("paid")]
# [1] 300
or
library(dplyr)
df %>% filter(desc=="bronchitis") %>% select(paid)
# filter refers to the row condition
# select filters the output column(s)
# > df %>% filter(desc=="bronchitis") %>% select(paid)
# paid
# 1 300

Answer 2

Using data.table
library(data.table)#v1.9.5+
setkey(setDT(df1), Description)[.('Bronchitis'),'Paid', with=FALSE]
# Paid
#1: $500
#2: $20.50
data
df1 <- structure(list(ex = c("Description", "Bronchitis",
"Complication of Pregnancy/Childbirth",
"Burns", "Bronchitis", "Ashtma"), data = c("val", "1.5", "2.2",
"3.3", "4.4", "1.2")), .Names = c("ex", "data"), class = "data.frame",
row.names = c("Paid", "$500", "$3,250", "$5,400", "$20.50", "$24"))