R: Assign Variable Names based on a matrix's columns -

i (very) new user r, , trying replicate matlab codes here (prefer r octave @ stage).

i have following matrix df:

variable value th   100 tw   100 gap  30 

i'd able assign variables, based on first column, values in second. basically, th = 100, tw = 100, gap = 30.

my end aim able manipulate data in following manner:

difference <- th-gap 

edit:

>dput(df) structure(list(s = structure(1:3, .label = c("aa", "bb", "cc" ), class = "factor"), n = c(2, 3, 5)), .names = c("s", "n"), row.names = c(na, -3l), class = "data.frame") 

you have adata.frame different object entirely matrix. matrix atomic vector dimension attributes wrap matrix. atomic vector matrix can contain data of single type, cannot have character data mixed numeric data. data.frame on other hand type of list, each list element atomic vector of same length (the length gives number of rows, number of elements in list number of columns). each list element can hold data of different type.

so lets assume have data.frame...

#  construct data df <- read.table( text = "variable value th   100 tw   100 gap  30" , h = true )  df #  variable value #1       th   100 #2       tw   100 #3      gap    30  #  subset data.frame values want using `[` operator difference <- df[ df$variable == 'th' , 'value' ] - df[ df$variable == 'gap' , 'value' ] #[1] 70 

we can subset data.frame using [ operator. first argument inside [,] refers rows , second argument columns. [ df$variable == 'th' , 'value' ] returns logical vector in rows argument true when variable == 'th' , returns rows meet condition column called value.