On Sep 5, 2009, at 11:58 AM, John Casey wrote:
Hello all,
I am new to R but have some experience with MATLAB and am trying
to make the switch. I generally find the two languages easy to adapt
but there are a few routine tasks which I would like to run smoother
in R and I am having trouble finding a help resource. Could someone
suggest a guide to filtering, selecting, sorting, and processing
biological matrix data? Here is a rudimentary example of what I'm
after [ocean research cruise- data.frame<-example]:
Cruise, dec yr, station, cast, depth, data1
1, 2007.65, 9, 29, 1, 105.04
1, 2007.65, 9, 29, 10, 104.91
1, 2007.65, 9, 29, 20, 101.43
1, 2007.65, 9, 29, 50, 100.68
1, 2007.65, 9, 29, 100, 100.09
1, 2007.69, 11, 33, 1, 107.32
1, 2007.69, 11, 33, 10, 105.94
1, 2007.69, 11, 33, 20, 102.19
1, 2007.69, 11, 33, 50, 101.27
1, 2007.69, 11, 33, 100, 100.15
Let's say I would like to select data1 from cast 33 at 1, 20, and
100m depth... how would I go about this?
?subset
subset(df1, cast==33 & depth %in% c(1,20,100) )
... or since your specification was vague;
subset(df1, cast==33 & depth==1 )
subset(df1, cast==33 & depth==20 )
subset(df1, cast==33 & depth==100 )
Also:
?"["
# the first column specification can be a logical vector, as in
df1[df1$col1 == 20, ] and will return subsets. But subset function is
nicer in that you don't have precede each column name by the dataframe
name.
And of course:
Thanks in advance for helping out a greenhorn!
John
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David Winsemius, MD
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