[R] How to find values that correspond to a given value (i.e. max)

William Dunlap wdunlap at tibco.com
Thu Sep 19 02:22:02 CEST 2013 

I would stay away from learning about 'while' and 'if' until you
understand using '[' to select subsets.  Subsetting is in chapter 2
of "An Introduction to R" and 'while' and 'if' are in chapter 9 for
good reason.

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com


> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf
> Of Hal_V
> Sent: Wednesday, September 18, 2013 3:23 PM
> To: r-help at r-project.org
> Subject: Re: [R] How to find values that correspond to a given value (i.e. max)
> 
> Thanks a lot to you both.
> Both solutions work great, and thanks to will for explaining how this
> works. I will have a look into while and if statements in R tomorrow...
> 
> 
> 2013/9/18 William Dunlap [via R] <ml-node+s789695n4676466h90 at n4.nabble.com>
> 
> > > If I have this:
> > >
> > > "names" <- c("John", "Jim", "Mary", "Susan")
> > > "age" <- c(16, 25, 32, 56)
> > > "income" <- c(2000, 3000, 2500, 1500)
> > > "all"<- data.frame(names, age, income)
> >
> > First, things will be easier for you if you make that dataset as
> >    all <- data.frame(
> >                        names = c("John", "Jim", "Mary", "Susan"),
> >                        age = c(16, 25, 32, 56),
> >                        income = c(2000, 3000, 2500, 1500))
> > so you don't have two things called "names", etc., one in the data.frame
> > and one in the current environment.
> >
> > You can select subsets in R using the "[" operator.  If it is given an
> > integer
> > argument it gives you the items indexed by that that integer vector; if
> > given a logical argument it gives you the items corresponding to TRUE's
> > in that logical vector.  E.g., try
> >    x <- c(11,22,33,44)
> >    x[c(1,3)] # gives 11 and 33
> >    x[c(TRUE, FALSE, TRUE, FALSE)] # also gives 11 and 33
> >
> > Make a logical vector of showing which items in 'income' are equal to
> > its maximum with
> >    atMaxIncome <- max(all$income) == all$income # gives, FALSE TRUE FALSE
> > FALSE
> > and do the selection with
> >    all[ atMaxIncome, ]
> >
> > > I tried some if-statements, but they didn't work because my programming
> > > skills outside of SQL are basically non-existent.
> >
> > All of this is in Chapter 2 of "An Introduction to R" (about 4 pages into
> > it), which comes with R.
> > Read it and do the examples and your R programming skills will improve.
> >
> > Bill Dunlap
> > Spotfire, TIBCO Software
> > wdunlap tibco.com
> >
> > > -----Original Message-----
> > > From: [hidden
> email]<http://user/SendEmail.jtp?type=node&node=4676466&i=0>[mailto:[hidden
> > email] <http://user/SendEmail.jtp?type=node&node=4676466&i=1>] On Behalf
> > > Of Hal_V
> > > Sent: Wednesday, September 18, 2013 12:43 PM
> > > To: [hidden email]<http://user/SendEmail.jtp?type=node&node=4676466&i=2>
> > > Subject: [R] How to find values that correspond to a given value (i.e.
> > max)
> > >
> > > Hi everyone
> > > I'm new to R, so this is probably a stupid question, but I looked around
> > for
> > > quite a while an couldn't find an answer. Basically I'm trying to print
> > > values that correspond to a found maximum.
> > >
> > > If I have this:
> > >
> > > "names" <- c("John", "Jim", "Mary", "Susan")
> > > "age" <- c(16, 25, 32, 56)
> > > "income" <- c(2000, 3000, 2500, 1500)
> > > "all"<- data.frame(names, age, income)
> > > max(all$income)
> > >
> > > I would like to print the name and age that correspond to the found
> > maximum.
> > > I tried some if-statements, but they didn't work because my programming
> > > skills outside of SQL are basically non-existent.
> > >
> > > I'd be glad for any pointers, thanks
> > >
> > >
> > >
> > > --
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