On Dec 6, 2008, at 11:30 AM, Edwin Sendjaja wrote:
> Hi,
>
> I have a table for an 1 week exam result for many classes in school,
> like
> this:
>
> Day Class_ID Test Result
> 1 Monday 1 Paper Passed
> 2 Tuesday 1 Oral Passed
> 3 Friday 1 Paper Passed
> 4 Monday 3 Paper Passed
> 5 Sunday 3 Oral Passed
> 6 Monday 3 Paper Passed
> 6 Sunday 3 Paper Passed
>
> How can I sum the Word "Passed" from Result column ( for earch
> Class_ID and
> each Test), so i can get this following table:
>
>
> Class_ID Test Passed_Count
> 1 1 Paper 2
> 2 1 Oral 1
> 3 3 Oral 1
> 4 3 Paper 3
Try
> xtabs( formula= ~ Test + Class_ID, data=cdat)
Class_ID
Test 1 3
Oral 1 1
Paper 2 3
> as.data.frame(xtabs( formula= ~ Test + Class_ID, data=cdat))
Test Class_ID Freq
1 Oral 1 1
2 Paper 1 2
3 Oral 3 1
4 Paper 3 3
This does not really sum the "Passed" column but rather counts the
number of entries (which all happen to be "Passed" in your example
data. (You also offered a data set with duplicate row numbers which
was corrected.) Had you offered a dataset in which Result were
somewhat more interesting, then counting the number of Passed might
have required putting (Result=="Passed") on the left side of the
formula.
--
David Winsemius
>
>
>
> Passed_Count column is just the Value, how many people passed the
> exam. In the
> tabell, they are 2 people passed the paper test (Result=Passed).
>
>
> I hope someone can help me, Or maybe there is an example that i can
> see.
>
>
> Thank you in advance
>
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