[R] Calculate depth from regular xyz grid for any coordinate within the grid

[MacQueen, Don]

I believe the interpp() function from the akima package will do what you
want.

-Don

-- 
Don MacQueen

Lawrence Livermore National Laboratory
7000 East Ave., L-627
Livermore, CA 94550
925-423-1062





On 7/28/14, 6:07 AM, "Kulupp" <kulupp at online.de> wrote:

>Dear R-experts,
>
>I have a regular grid dataframe (here: the first 50 rows) :
>
># data frame (regular grid) with x, y (UTM-coordinates) and z (depth)
># x=UTM coordinates (easting, zone 32)
># y=UTM coordinates (northing, zone 32)
># z=river-depth (meters)
>df <- data.frame(x=c(3454240, 3454240, 3454240, 3454240, 3454240,
>3454250, 3454250, 3454250, 3454250, 3454250, 3454250, 3454250, 3454250,
>3454250, 3454250, 3454250,
>                      3454250, 3454250, 3454260, 3454260, 3454260,
>3454260, 3454260, 3454260, 3454260, 3454260, 3454260, 3454260, 3454260,
>3454260, 3454260, 3454260,
>                      3454260, 3454260, 3454260, 3454260, 3454260,
>3454260, 3454260, 3454260, 3454270, 3454270, 3454270, 3454270, 3454270,
>3454270, 3454270, 3454270,
>                      3454270, 3454270),
>                  y=c(5970610, 5970620, 5970630, 5970640, 5970650,
>5970610, 5970620, 5970630, 5970640, 5970650, 5970660, 5970670, 5970680,
>5970690, 5970700, 5970710,
>                      5970720, 5970730, 5970610, 5970620, 5970630,
>5970640, 5970650, 5970660, 5970670, 5970680, 5970690, 5970700, 5970710,
>5970720, 5970730, 5970740,
>                      5970750, 5970760, 5970770, 5970780, 5970790,
>5970800, 5970810, 5970820, 5970610, 5970620, 5970630, 5970640, 5970650,
>5970660, 5970670, 5970680,
>                      5970690, 5970700),
>                  z= c(-1.5621, -1.5758, -1.5911, -1.6079, -1.6247,
>-1.5704, -1.5840, -1.5976, -1.6113, -1.6249, -1.6385, -1.6521, -1.6658,
>-1.6794, -1.6930, -1.7067,
>                       -1.7216, -1.7384, -1.5786, -1.5922, -1.6059,
>-1.6195, -1.6331, -1.6468, -1.6604, -1.6740, -1.6877, -1.7013, -1.7149,
>-1.7285, -1.7422, -1.7558,
>                       -1.7694, -1.7831, -1.7967, -1.8103, -1.8239,
>-1.8376, -1.8522, -1.8690, -1.5869, -1.6005, -1.6141, -1.6278, -1.6414,
>-1.6550, -1.6686, -1.6823,
>                       -1.6959, -1.7095))
>head(df)
>plot(df[,1:2], las=3)   # to show that it's a regular grid
>
>My question: is there a function to calculate the depth of any
>coordinate pair (e.g. x=3454263, y=5970687) within the grid, e.g. by
>bilinear interpolation or any other meaningful method?
>
>Thanks a lot for your help in anticipation
>
>Best wishes
>
>Thomas
>
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