[R] Data Structure to Code

[R. Michael Weylandt]

You said something about extracting January to June -- that's not so
possible with the default ts (best I understand it): ts() only allows
regular time-series so you can't go jan to jun at 1 month intervals
and then jump to jan again (6 months). If you want irregular time
series, check out the zoo package.

You're getting an "invalid parameters" error because the time window
specified is too short for the length of data given -- the .Tsp
attribute gives the start, end, and number of samples per year. This
works:

structure(c(112, 118, 132, 129, 121, 135, 148, 148, 136, 119,
104, 118, 115, 126, 141, 135, 125, 149, 170, 170, 158, 133, 114,
140, 145, 150, 178, 163, 172, 178, 199, 199, 184, 162, 146, 166,
171, 180, 193, 181, 183, 218, 230, 242, 209, 191, 172, 194, 196,
196, 236, 235, 229, 243, 264, 272, 237, 211, 180, 201, 204, 188,
235, 227, 234, 264, 302, 293, 259, 229, 203, 229, 242, 233, 267,
269, 270, 315, 364, 347, 312, 274, 237, 278, 284, 277, 317, 313,
318, 374, 413, 405, 355, 306, 271, 306, 315, 301, 356, 348, 355,
422, 465, 467, 404, 347, 305, 336, 340, 318, 362, 348, 363, 435,
491, 505, 404, 359, 310, 337, 360, 342, 406, 396, 420, 472, 548,
559, 463, 407, 362, 405, 417, 391, 419, 461, 472, 535, 622, 606,
508, 461, 390, 432), .Tsp = c(1949, 1972.83333333333, 6), class =
"ts") ## Note it ends later

Also, it's probably not a good idea to emulate the output of dput() to
set up new input. That's what constructor functions -- like ts()  or
zoo() --  are for.

Michael

On Sun, Jan 29, 2012 at 11:36 AM, Ajay Askoolum <aa2e72e at yahoo.co.uk> wrote:
> Thank you. I need some clarification.
>
> dput(AirPassengers)
>
> gives:
>
> structure(c(112, 118, 132, 129, 121, 135, 148, 148, 136, 119,
> 104, 118, 115, 126, 141, 135, 125, 149, 170, 170, 158, 133, 114,
> 140, 145, 150, 178, 163, 172, 178, 199, 199, 184, 162, 146, 166,
> 171, 180, 193, 181, 183, 218, 230, 242, 209, 191, 172, 194, 196,
> 196, 236, 235, 229, 243, 264, 272, 237, 211, 180, 201, 204, 188,
> 235, 227, 234, 264, 302, 293, 259, 229, 203, 229, 242, 233, 267,
> 269, 270, 315, 364, 347, 312, 274, 237, 278, 284, 277, 317, 313,
> 318, 374, 413, 405, 355, 306, 271, 306, 315, 301, 356, 348, 355,
> 422, 465, 467, 404, 347, 305, 336, 340, 318, 362, 348, 363, 435,
> 491, 505, 404, 359, 310, 337, 360, 342, 406, 396, 420, 472, 548,
> 559, 463, 407, 362, 405, 417, 391, 419, 461, 472, 535, 622, 606,
> 508, 461, 390, 432), .Tsp = c(1949, 1960.91666666667, 12), class = "ts")
>
> and AirPassengers looks as follows:
>
> AirPassengers
>      Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
> 1949 112 118 132 129 121 135 148 148 136 119 104 118
> 1950 115 126 141 135 125 149 170 170 158 133 114 140
> 1951 145 150 178 163 172 178 199 199 184 162 146 166
> 1952 171 180 193 181 183 218 230 242 209 191 172 194
> 1953 196 196 236 235 229 243 264 272 237 211 180 201
> 1954 204 188 235 227 234 264 302 293 259 229 203 229
> 1955 242 233 267 269 270 315 364 347 312 274 237 278
> 1956 284 277 317 313 318 374 413 405 355 306 271 306
> 1957 315 301 356 348 355 422 465 467 404 347 305 336
> 1958 340 318 362 348 363 435 491 505 404 359 310 337
> 1959 360 342 406 396 420 472 548 559 463 407 362 405
> 1960 417 391 419 461 472 535 622 606 508 461 390 432
>
> Where are the column headers in the result of dput(AirPassengers)?
>
> I guess it must be something to do with the '12' in the final argument of
> .Tsp.
>
> So, If I just wanted 'Jan' ... 'Jun' and specified the following:
>
>
> structure(c(112, 118, 132, 129, 121, 135, 148, 148, 136, 119,
> 104, 118, 115, 126, 141, 135, 125, 149, 170, 170, 158, 133, 114,
> 140, 145, 150, 178, 163, 172, 178, 199, 199, 184, 162, 146, 166,
> 171, 180, 193, 181, 183, 218, 230, 242, 209, 191, 172, 194, 196,
> 196, 236, 235, 229, 243, 264, 272, 237, 211, 180, 201, 204, 188,
> 235, 227, 234, 264, 302, 293, 259, 229, 203, 229, 242, 233, 267,
> 269, 270, 315, 364, 347, 312, 274, 237, 278, 284, 277, 317, 313,
> 318, 374, 413, 405, 355, 306, 271, 306, 315, 301, 356, 348, 355,
> 422, 465, 467, 404, 347, 305, 336, 340, 318, 362, 348, 363, 435,
> 491, 505, 404, 359, 310, 337, 360, 342, 406, 396, 420, 472, 548,
> 559, 463, 407, 362, 405, 417, 391, 419, 461, 472, 535, 622, 606,
> 508, 461, 390, 432), .Tsp = c(1949, 1972, 6), class = "ts")
>
>
> Why does this generate " invalid time series parameters specified"?
>
>
>
>
>