Question about datatypes/plotting issue

library(zoo)
as.yearmon("January 1987", "%B %Y")

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

David Winsemius, MD
Heritage Laboratories
West Hartford, CT