[R] gridding values in a data frame

[hadley wickham]

It's hard to check without a reproducible example, but the following
code should give you a 3d array of lat x long x time:

library(reshape)

df$lat <- round_any(df$LATITUDE, 5)
df$long <- round_any(df$LONGITUDE, 5)
df$value <- df$TIME

cast(df, lat ~ long ~ time, mean)


On Thu, Apr 30, 2009 at 10:55 AM, dxc13 <dxc13 at health.state.ny.us> wrote:
>
> Hi all,
> I have a data frame that looks like such:
> LATITUDE   LONGITUDE   TEMPERATURE   TIME
> 36.73         -176.43        58.32               1
> 50.95            90.00        74.39               1
> -30.42            5.45        23.26               1
> 15.81         -109.31        52.44               1
> -80.75        -144.95        66.19              2
> 90.00          100.55        37.50               2
> 65.41         -4.49           29.83               2
>
> and this goes on for a A LOT more records, until time=1200
>
> I want to create a 5 degree by 5 degree grid of this data, with the value of
> temperature in the appropriate grid cell.  I want one grid for each time
> value.  For each time value, this works out to be a 36x72 grid with 2592
> cells because the longitude spans -180 to 180 and latitude spans 90 to -90
> and they would be in increments of 5 degrees.  If there are no temperatures
> available to be put into a grid cell, than that cell should get a missing
> value, NA, put into it.
> Also, could the gridded result for each time be written to a text file
> before processing the next time value?
>
> Hope this is clear.
> Thanks in advance.
>
> dxc13
> --
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