how to count number of occurrences
Is the following what you want? It should give the number of "X"s immediately preceding each "Y".
samp <- c("X", "Y", "X", "X", "X", "X", "Y", "Y", "Y", "Y", "X", "X",
"X", "X", "X", "Y", "Y", "Y", "Y", "Y")
diff((seq_along(samp) - cumsum(samp=="Y"))[samp=="Y"])
[1] 4 0 0 0 5 0 0 0 0 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 Sl K
Sent: Wednesday, November 02, 2011 9:55 AM
To: r-help at r-project.org
Subject: [R] how to count number of occurrences
Dear R users,
I have this data frame,
y samp
8 0.03060419 X
18 0.06120838 Y
10 0.23588374 X
3 0.32809965 X
1 0.36007100 X
7 0.36730571 X
20 0.47176748 Y
13 0.65619929 Y
11 0.72014201 Y
17 0.73461142 Y
6 0.76221313 X
2 0.77005691 X
4 0.92477243 X
9 0.93837591 X
5 0.98883581 X
16 1.52442626 Y
12 1.54011381 Y
14 1.84954487 Y
19 1.87675183 Y
15 1.97767162 Y
and I am trying to find the number of X's that occur before ith Y occurs.
For example, there is 1 X before the first Y, so I get 1. There are 4 X's
before the second Y, so I get 4, there is no X between second and third Y,
so I get 0 and so on. Any hint to at least help me to start this will be
appreciated. Thanks a lot!
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