[R] Question about datatypes/plotting issue
Oscar Bonilla
obonilla at galileo.edu
Wed Mar 11 17:48:48 CET 2009
David,
I struggled with this for a while. I think the problem with the dates
I have is that they are not specific dates, they are "partial" dates.
A workaround for that that I got from someone else in the list was:
as.Date(paste(x$Date, '1'), '%B %Y %d')
to make them specific dates (the first of the month).
Cheers,
-Oscar
On Mar 10, 2009, at 7:58 PM, David Winsemius wrote:
> You need to convert W$Date into a real date variable. At the moment
> it is just a character variable.
>
> > str(W)
> 'data.frame': 265 obs. of 23 variables:
> $ Date : Factor w/ 265 levels " ","April 1987",..: 1 90
> 68 156 2 178 134 ...
> $ AZ.Phoenix : Factor w/ 236 levels "","100.00","100.43",..:
> 236 1 1 1 1 1 1 1 1 1 ...
> $ CA.Los.Angeles : Factor w/ 260 levels "100.00","100.02",..: 260
> 113 114 115 116 ...
> $ CA.San.Diego : Factor w/ 261 levels "100.00","101.07",..: 261
> 109 110 111 112 ...
> $ CA.San.Francisco: Factor w/ 256 levels "100.00","102.70",..: 256
> 108 109 110 111 ...
> .(output trimmed)
> .
> .
> ?Date # not the variable name, the R class name
> ?format.Date
> ?strptime
>
> Unfortunately I seem to be at one of the many limits to my knowledge:
> This code behaves in the manner I expected:
>
> > format(Sys.time(), "%a %b %d %X %Y %Z")
> [1] "Tue Mar 10 22:19:28 2009 EDT"
> > strptime(format(Sys.time(), "%a %b %d %X %Y %Z"), format="%a %b %d
> %X %Y %Z")
> [1] "2009-03-10 22:20:04"
>
> Whereas this code does not:
> > format(Sys.Date(), "%B %Y")
> [1] "March 2009"
> > as.Date(format(Sys.Date(), "%B %Y"), "%B %Y")
> # would have assumed one was the inverse of the other, but ...
>
> [1] NA
>
> For some reason I cannot get the space delimited Month-YYYY combo to
> convert. I can getother space delimited formats to work for input
> or output:
> > as.Date("03 1998", "%M %Y")
> [1] "1998-03-10"
>
> > format(Sys.Date(), "%B %Y")
> [1] "March 2009"
>
> Puzzled;
> --
> David Winsemius
>
> On Mar 10, 2009, at 9:15 PM, Oscar Bonilla wrote:
>
>> Hi,
>>
>> I am trying to plot the Case-Shiller index found at: http://www2.standardandpoors.com/spf/pdf/index/CSHomePrice_History_022445.xls
>>
>> The way I'm importing it into R is as follows:
>>
>> library(gdata)
>> W <- read.xls("http://www2.standardandpoors.com/spf/pdf/index/CSHomePrice_History_022445.xls
>> ", header=TRUE)
>> attach(W)
>>
>> To give you and idea of what the data looks like:
>>
>> > head(W)
>> Date AZ.Phoenix CA.Los.Angeles CA.San.Diego CA.San.Francisco
>> 1 PHXR LXXR SDXR
>> SFXR
>> 2 January 1987 59.33 54.67
>> 46.61
>> 3 February 1987 59.65 54.89
>> 46.87
>> 4 March 1987 59.99 55.16
>> 47.32
>> 5 April 1987 60.81 55.85
>> 47.69
>> 6 May 1987 61.67 56.35
>> 48.31
>> CO.Denver DC.Washington FL.Miami FL.Tampa GA.Atlanta IL.Chicago
>> MA.Boston
>> 1 DNXR WDXR MIXR TPXR ATXR
>> CHXR BOXR
>> 2 50.20 64.11 68.50 77.33
>> 53.55 70.04
>> 3 49.96 64.77 68.76 77.93
>> 54.64 70.08
>> 4 50.15 65.71 69.23 77.76
>> 54.80 70.00
>> 5 50.55 66.40 69.20 77.56
>> 54.88 70.70
>> 6 50.63 67.27 69.46 77.85
>> 55.43 71.51
>> MI.Detroit MN.Minneapolis NC.Charlotte NV.Las.Vegas NY.New.York
>> OH.Cleveland
>> 1 DEXR MNXR CRXR LVXR
>> NYXR CEXR
>> 2 63.39 66.36
>> 74.42 53.53
>> 3 63.94 67.03
>> 75.43 53.50
>> 4 64.17 67.34
>> 76.25 53.68
>> 5 64.81 67.88
>> 77.34 53.75
>> 6 65.18 67.90
>> 79.16 54.71
>> OR.Portland TX.Dallas WA.Seattle Composite.10 Composite.20
>> 1 POXR DAXR SEXR CSXR SPCS20R
>> 2 41.05 62.82
>> 3 41.28 63.39
>> 4 41.06 63.87
>> 5 40.96 64.57
>> 6 41.24 65.56
>>
>>
>> Now on to the problem... if I just run
>>
>> plot(CA.San.Francisco ~ Date)
>>
>> I get:
>> <pastedGraphic.png>
>>
>> Which I suspect is a problem because the Date column is not really
>> a Date, it is a "factor"
>>
>> > class(Date)
>> [1] "factor"
>>
>> If I run:
>> plot(as.numeric(CA.San.Francisco), type="l")
>>
>> I get:
>>
>> <pastedGraphic.png>
>>
>>
>> which is wrong, as CA.San.Francisco has no such discontinuity.
>>
>> > CA.San.Francisco
>> [1] SFXR 46.61 46.87 47.32 47.69 48.31 48.83 49.49 49.94
>> 50.69
>> [11] 51.33 51.80 52.03 52.24 52.64 53.19 54.19 56.09 58.22
>> 58.70
>> [21] 59.00 59.50 60.37 61.31 62.20 62.66 63.32 64.64 66.27
>> 67.77
>> [31] 69.26 70.27 71.36 72.31 72.95 73.25 73.02 72.87 72.95
>> 73.50
>> [41] 74.57 75.12 75.15 74.81 74.45 74.24 73.44 72.58 71.47
>> 71.17
>> [51] 70.27 69.56 69.46 70.13 70.83 71.39 71.52 71.55 71.21
>> 70.69
>> [61] 70.05 69.67 69.48 69.17 69.26 69.86 70.02 70.00 69.64
>> 69.51
>> [71] 69.28 68.85 68.21 67.77 67.44 67.09 67.59 67.90 67.99
>> 67.65
>> [81] 67.63 67.50 67.18 66.77 66.27 65.98 65.79 66.37 67.05
>> 67.70
>> [91] 68.15 68.38 68.40 68.21 68.17 68.04 67.93 67.73 67.40
>> 66.79
>> [101] 67.08 67.31 67.50 67.72 67.78 67.76 67.30 66.80
>> 66.43 66.15
>> [111] 65.97 65.92 66.44 67.05 67.67 68.02 68.35 68.43
>> 68.53 68.72
>> [121] 68.69 68.80 68.81 69.78 71.09 72.19 73.12 73.75
>> 74.43 74.76
>> [131] 75.22 75.31 75.81 76.19 76.53 77.48 79.08 80.82
>> 82.41 83.52
>> [141] 84.41 85.06 85.05 84.66 84.50 85.03 85.93 87.51
>> 89.21 90.82
>> [151] 92.52 94.20 95.14 96.15 96.72 97.87 98.90 100.00
>> 102.70 106.56
>> [161] 110.97 115.01 118.45 119.48 119.95 120.94 123.08 125.66
>> 128.58 131.16
>> [171] 133.27 134.10 134.38 134.09 132.64 130.95 129.15 128.60
>> 128.01 126.99
>> [181] 125.47 125.13 126.06 128.79 132.62 136.07 139.35 141.02
>> 141.93 142.29
>> [191] 142.74 143.06 142.40 141.90 142.19 143.00 144.69 145.53
>> 146.53 147.75
>> [201] 148.72 150.25 151.75 153.36 154.62 155.93 158.11 160.90
>> 164.65 167.76
>> [211] 171.51 173.85 175.89 178.15 180.75 183.15 185.72 189.35
>> 193.50 198.30
>> [221] 201.86 205.52 208.92 211.56 212.86 214.73 215.55 215.70
>> 215.11 214.78
>> [231] 215.50 216.04 217.52 218.37 218.12 217.63 217.22 216.37
>> 215.42 213.84
>> [241] 212.13 211.78 210.78 211.09 211.47 210.89 209.48 208.64
>> 208.15 206.46
>> [251] 202.03 195.49 189.23 183.81 174.54 168.38 164.63 162.70
>> 159.83 156.88
>> [261] 151.42 145.53 139.44 135.28 130.12
>> 256 Levels: 100.00 102.70 106.56 110.97 115.01 118.45 119.48
>> 119.95 ... SFXR
>>
>> However, as.numeric(CA.San.Francisco) does have it!
>>
>> > as.numeric(CA.San.Francisco)
>> [1] 256 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122
>> 123 124
>> [19] 125 126 127 128 129 130 131 132 133 134 140 164 185 199 205
>> 211 214 217
>> [37] 215 213 214 219 224 227 228 226 223 221 218 212 207 203 199
>> 190 187 198
>> [55] 201 206 208 209 204 200 197 192 188 184 185 194 196 195 191
>> 189 186 183
>> [73] 173 164 154 149 156 166 168 158 157 155 150 144 140 138 135
>> 141 147 160
>> [91] 171 175 176 173 172 170 167 162 153 145 148 152 155 161 165
>> 163 151 146
>> [109] 142 139 137 136 143 147 159 169 174 177 178 180 179 181 182
>> 193 202 210
>> [127] 216 220 222 225 229 230 231 232 233 234 235 236 237 238 239
>> 244 243 241
>> [145] 240 242 245 246 247 248 249 250 251 252 253 254 255 1 2
>> 3 4 5
>> [163] 6 7 8 9 10 13 17 23 26 28 29 27 25 22 20
>> 18 16 15
>> [181] 12 11 14 19 24 31 32 34 36 38 40 42 39 35 37
>> 41 43 44
>> [199] 45 46 47 48 50 51 52 53 55 57 60 61 63 64 66
>> 67 68 69
>> [217] 71 73 74 76 77 79 83 89 92 94 99 100 96 95 98
>> 101 104 107
>> [235] 106 105 103 102 97 93 91 90 85 87 88 86 84 82 81
>> 80 78 75
>> [253] 72 70 65 62 59 58 56 54 49 44 33 30 21
>>
>> What I'd like to get, is a graph like this (the red line):
>>
>> <pastedGraphic.png>
>>
>> I'm really puzzled about what's going on here. Any help would be
>> greatly appreciated.
>>
>> Thanks,
>>
>> -Oscar
>>
>> ______________________________________________
>> R-help at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>
> David Winsemius, MD
> Heritage Laboratories
> West Hartford, CT
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