Hi,
Following please find *some* of my data.
percent quiz group
100 1 High
100 1 High
100 1 High
25 1 Low
50 1 Low
75 1 High
50 1 Low
75 1 High
100 1 High
100 1 High
50 1 Low
60 2 High
20 2 High
100 2 High
60 2 Low
40 2 Low
80 2 High
20 2 Low
60 2 High
40 2 High
100 2 High
90 3 High
100 3 High
0 3 High
90 3 Low
80 3 High
60 3 Low
100 3 High
60 3 High
Here is the by command i used:
by(percent, quiz, function(percent) {t.test(percent~group,
data=marks.long)})
Basically it gave me three of the same t.tests based on the full data
set, not the subsets (quiz 1, 2 and 3).
So far it seems like my method is more straightforward!
Julian Burgos wrote:
> Could you post some of your data and your initial test, and explain
> why it didn't worked? It is difficult to figure out what is the
> problem with your call to by().
>
> Julian
>
> Matthew Dubins wrote:
>> I've tried to use by(), but the closest i got to it doing what I
>> wanted was using the following:
>>
>> by(percent, quiz, function(percent) {t.test(percent~group,
>> data=marks.long)})
>>
>> But the results it gave me weren't t.tests of percent by group
>> according to quiz number.
>>
>>
>> Julian Burgos wrote:
>>> See by()
>>>
>>> Matthew Dubins wrote:
>>>> Hi all,
>>>>
>>>> I wrote a simple function that gives me multiple t.test results
>>>> according to a subset variable and am wondering whether or not I
>>>> reinvented the wheel. Observe:
>>>>
>>>> t.test.sub <- function (formula, data, sub, ...)
>>>> {
>>>> for(i in 1:max(sub))
>>>> {
>>>> print(t.test(formula, data = subset(data, sub ==
>>>> i), ...))
>>>> }
>>>> }
>>>>
>>>> Is there already a similar function in some package?
>>>>
>>>> Thanks,
>>>> Matthew Dubins
>>>>
>>>> ______________________________________________
>>>> R-help@r-project.org mailing list
>>>> https://stat.ethz.ch/mailman/listinfo/r-help
>>>> PLEASE do read the posting guide
>>>> http://www.R-project.org/posting-guide.html
>>>> and provide commented, minimal, self-contained, reproducible code.
>>>
>>
>
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