Re: [R] zoo object: replace NAs from another zoo object

From: Timothy W. Hilton <hilton_at_meteo.psu.edu>
Date: Fri, 14 Mar 2008 06:16:45 -0400

Gabor,

Many thanks for your suggestion. This solution is very close, but not exactly what I had in mind, because na.omit removes the entire row in which an NA appears. I want to replace values in old with non-NA values from corresponding times in new. If a timestamp from old does not appear in new, or appears but the new value is NA, then I want to keep the old value. That is, I want to write mergeOldNew(old, new) to get the following result:

> new

                         P    PAR pcp

(05/20/06 00:00:00) 956.23 252.30 NA
(05/20/06 00:02:00) NA 244.85 NA
(05/20/06 00:04:00) NA 236.45 NA
> old P PAR pcp
(05/19/06 23:58:00) NA NA NA
(05/20/06 00:00:00) NA NA NA
(05/20/06 00:02:00) 955.68 311.54 0
(05/20/06 00:04:00) 955.70 320.74 0
(05/20/06 00:06:00) 955.68 309.16 0
(05/20/06 00:08:00) 955.69 301.72 0

> mergeOldNew(old, new)

(05/19/06 23:58:00) NA NA NA
(05/20/06 00:00:00) 956.23 252.30 NA
(05/20/06 00:02:00) 955.68 244.85 0
(05/20/06 00:04:00) 955.70 236.45 0
(05/20/06 00:06:00) 955.68 309.16 0
(05/20/06 00:08:00) 955.69 301.72 0

Looping your suggestion over the individual columns in old and new works, but I wonder if there is a more elegant solution to avoid the loop?

Many thanks for your help. dput output for old and new are below.

-Tim


> dput(old)
structure(c(NA, NA, 955.68, 955.7, 955.68, 955.69, NA, NA, 311.54, 320.74, 309.16, 301.72, NA, NA, 0, 0, 0, 0), .Dim = c(6L, 3L), .Dimnames = list(

    c("13679", "13680", "13681", "13682", "13683", "13684"),     c("P", "PAR", "pcp")), index = structure(c(13287.9986111111, 13288, 13288.0013888889, 13288.0027777778, 13288.0041666667, 13288.0055555556), format = structure(c("m/d/y", "h:m:s"), .Names = c("dates", "times")), origin = c(1, 1, 1970), class = c("chron", "dates", "times")), class = "zoo")

> dput(new)
structure(c(956.23, NA, NA, 252.3, 244.85, 236.45, NA, NA, NA
), .Dim = c(3L, 3L), .Dimnames = list(c("1", "2", "3"), c("P", "PAR", "pcp")), index = structure(c(13288, 13288.0013888889, 13288.0027777778), format = structure(c("m/d/y", "h:m:s"), .Names = c("dates", "times")), origin = c(1, 1, 1970), class = c("chron", "dates", "times")), class = "zoo")




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