[R] How to adjust the start of a series to zero? (i.e. subtract the first value from the sequence)
Phil Spector
spector at stat.berkeley.edu
Sun Jul 1 00:31:58 CEST 2012
Kristiina -
If the data will always be sorted so that the first time
for a point appears first in the data frame, you can use:
sort2v4$adj_mean = sort2v4$mean - ave(sort2v4$mean,sort2v4$point,FUN=function(x)x[1])
Otherwise, something like this should work:
firstmeans = subset(sort2v4,time==1,select=c(point,mean))
names(firstmeans)[2] = 'adj'
sort2v4 = merge(sort2v4,firstmeans)
sort2v4$adj_mean = with(sort2v4,mean-adj)
sort2v4$adj = NULL
In the future, you may want to learn about the dput function, which makes
it a little easier for others to reproduce your data.
- Phil Spector
Statistical Computing Facility
Department of Statistics
UC Berkeley
spector at stat.berkeley.edu
On Sat, 30 Jun 2012, Kristiina Hurme wrote:
> Hello,
> I'd have a time series, where I am plotting the means and sd of a distance
> for a variety of positions along a bird's bill. I'd like to set each line
> (represented by "point") to start at zero, so that I can look at the
> absolute change along the series. At the moment I only know how to do that
> in Excel, by subtracting the value of time 1, point 1 from all other times
> for point 1. My actual data set has many points ( 20 per bird, only 3 shown
> here), so I would love to make this faster in R. Ideally, I would have
> another column titled "adj_mean" for the adjusted means.
>
> Here is an example.
>
>> sort2v4
> point time mean sd
> 1 1 1 52.501000 1.5073927
> 3 1 2 54.501818 0.8510329
> 4 1 3 56.601739 1.5787222
> 5 1 4 57.200000 1.2292726
> 6 1 5 59.300000 2.2632327
> 7 1 6 57.800893 1.4745218
> 8 1 7 55.303508 2.2661855
> 9 1 8 51.100943 1.8540025
> 10 1 9 50.600000 1.7126977
> 2 1 10 52.904716 1.1010460
> 111 2 1 50.605963 1.2633969
> 113 2 2 52.203828 0.7890765
> 114 2 3 54.100909 1.1013344
> 115 2 4 55.000000 1.1547005
> 116 2 5 57.001725 1.6341500
> 117 2 6 55.003591 1.5652438
> 118 2 7 52.911089 1.7373914
> 119 2 8 49.204022 1.0350809
> 120 2 9 48.904103 0.8747568
> 112 2 10 50.915700 0.8765483
> 131 3 1 48.608228 0.8433913
> 133 3 2 49.307101 0.4827703
> 134 3 3 51.310824 0.9424023
> 135 3 4 52.413350 0.6997860
> 136 3 5 54.116723 1.1927297
> 137 3 6 52.618161 1.1686288
> 138 3 7 49.822764 1.6303473
> 139 3 8 47.107336 1.2013356
> 140 3 9 47.104214 1.1986148
> 132 3 10 48.719484 0.6765047
>
> and I would like it to look like this... (which I did in Excel). The start
> of each time 1-10 has an adj_mean of 0.
>> sort2v4
> point time mean sd adj_mean
> 1 1 1 52.501 1.5073927 0
> 3 1 2 54.501818 0.8510329 2.000818
> 4 1 3 56.601739 1.5787222 4.100739
> 5 1 4 57.2 1.2292726 4.699
> 6 1 5 59.3 2.2632327 6.799
> 7 1 6 57.800893 1.4745218 5.299893
> 8 1 7 55.303508 2.2661855 2.802508
> 9 1 8 51.100943 1.8540025 -1.400057
> 10 1 9 50.6 1.7126977 -1.901
> 2 1 10 52.904716 1.101046 0.403716
> 111 2 1 50.605963 1.2633969 0
> 113 2 2 52.203828 0.7890765 1.597865
> 114 2 3 54.100909 1.1013344 3.494946
> 115 2 4 55 1.1547005 4.394037
> 116 2 5 57.001725 1.63415 6.395762
> 117 2 6 55.003591 1.5652438 4.397628
> 118 2 7 52.911089 1.7373914 2.305126
> 119 2 8 49.204022 1.0350809 -1.401941
> 120 2 9 48.904103 0.8747568 -1.70186
> 112 2 10 50.9157 0.8765483 0.309737
> 131 3 1 48.608228 0.8433913 0
> 133 3 2 49.307101 0.4827703 0.698873
> 134 3 3 51.310824 0.9424023 2.702596
> 135 3 4 52.41335 0.699786 3.805122
> 136 3 5 54.116723 1.1927297 5.508495
> 137 3 6 52.618161 1.1686288 4.009933
> 138 3 7 49.822764 1.6303473 1.214536
> 139 3 8 47.107336 1.2013356 -1.500892
> 140 3 9 47.104214 1.1986148 -1.504014
> 132 3 10 48.719484 0.6765047 0.111256
>
> Thank you so much for your help.
> Kristiina
>
> --
> View this message in context: http://r.789695.n4.nabble.com/How-to-adjust-the-start-of-a-series-to-zero-i-e-subtract-the-first-value-from-the-sequence-tp4634999.html
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>
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