how apply a function across runs

2018-06-13 10:09:29

Possible Duplicate:
R Grouping functions: sapply vs. lapply vs. apply. vs. tapply vs. by vs. aggregate vs

I have a model output file which looks like:

run step x
1    1    1
1    2    4
1    3    3
1    1    4 
1    2    5
1    3    6
2    1    5
2    2    4
2    3    7
2    1    3

. . . and I need to calculate the mean values for each step according to the run number.How can I do this? Many thanks to anyone, who can help me. Viola

If I understand you correctly, this can be done using ddply from the plyr package:

require(plyr)
ddply(model_output, .(run, step), summarise, mn = mean(x))

Where model_output is the model output you read from file.

或者一个基本的R版本：

aggregate(test["x"],test[c("run","step")],mean)

  run step   x
1   1    1 2.5
2   2    1 4.0
3   1    2 4.5
4   2    2 4.0
5   1    3 4.5
6   2    3 7.0

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