[R] sequential input script dataframe process functionality

[William Dunlap]

Again, feed the output of menu() directly into "[".  Do not use switch().
Bill Dunlap
TIBCO Software
wdunlap tibco.com


On Mon, Sep 8, 2014 at 2:12 AM,  <rl at openmailbox.org> wrote:
> On Sat, 6 Sep 2014 08:21:19 -0700
> William Dunlap <wdunlap at tibco.com> wrote:
>
>> >
>> > testdataextract1<-switch(menu(c(unique(levels(testdata[,1]))),graphics=FALSE,title='Select
>> > something'))
>>
>> The switch function does not work the way you are expecting it to.
>> Read help("switch") and read the introduction to R that comes with R.
>>
>> You probably want to use the output of menu() to extract a row of
>> testdata with testdata[outputOfMenu,].  (How could testdataextract1
>> contain anything in the 2nd or 3rd columns of testdata if the
>> expression producing testdataextract1 does not contain any reference
>> to that column?)
>>
>
> I tried:
>
>> testdataextract1<-function (testdata) {
>
> +
> selectionresult<-switch(menu(c(unique(levels(testdata[,1]))),graphics=FALSE,title='Select
> something'))
> + return (testdata[selectionresult,])
> + }
>>
>> testdataextract1(testdata)
>
> Select something
>
> 1: text test1
> 2: text test2
> 3: text test3
>
> Selection: 2
> [1] variablea variableb variablec
> <0 rows> (or 0-length row.names)
>
> Why does this error occur?
>
> Although the menu must show only unique values to be chosen, the
> resultant output must show all values that match the chosen value in
> this example:
>
> text test2 other texty       200
> text test2 other texty       700
> text test2 other texty       300
> text test2 other texty       250