[R-sig-Geo] reclassify question

[Jordan Chamberlin]

Hi Ashton,

There are a few different ways to solve this.  See the reclassify help 
for clues, e.g. "You can also provide a two column matrix ("is", 
"becomes") which can be useful for integer values."

Alternatively, given how your reclassification table is currently set 
up, try specifying your reclassify operation as:

ecos = reclassify(testarea, recls, right=NA)

The "right=NA" argument should make each range open at both right and 
left boundaries. As it stands, 71 is not getting reclassified because 
the length of the classification is essentially zero (because the right 
boundary is closed).

Good luck!

Jordan

On 1/11/2014 9:44 PM, Ashton Drew wrote:
> I have just started switching from Arc to R for some of my spatial analyses
> and am stuck on a reclassification problem.  I am trying to use reclassify
> from the package raster.  I have been able to run the examples, but cannot
> run my own data.  I have tried to provide an example of my code using a
> small subset of my data.  The reclassify does work for some values (about
> 9/10 of the grid cells), but not all.  In the example below, values 71,
> 145, and 231 are not reclassified.
>
> The primary difference that I can find between my data and the worked
> examples is that all examples seem to assume that a range of values from
> continuous data are being reclassified, while my data are categorical
> (numerical codes for land cover classes).  Instead of a range to single
> value reclassification, I just want to reclassify each value to a single
> different value (in some cases, some of the original data can be treated as
> if they are a range, as shown in the example reclass matrix, but in reality
> this is not the case).  I thought maybe I could just put the same value in
> both the min and max columns, but that did not seem to work (value 71 in
> the example).  But that is not the only problem, because 145 and 231 are
> both values that I treated as if they were part of a range.  I do not get
> any error
> messages, just some values do not reclassify.
>
> So I am out of ideas.  If I cannot use reclassify, is there another way to
> classify ordinal or categorical raster data when I am not reclassifying a
> range to single value? Thank you for any help!
>
>> testarea
> class       : RasterLayer
> dimensions  : 34, 33, 1122  (nrow, ncol, ncell)
> resolution  : 30, 30  (x, y)
> extent      : 1200009, 1200999, 999992.1, 1001012  (xmin, xmax, ymin, ymax)
> coord. ref. : +proj=aea +lat_1=29.5 +lat_2=45.5 +lat_0=23 +lon_0=-96 +x_0=0
> +y_0=0 +ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs
> data source : in memory
> names       : segap_scope
> values      : 1, 231  (min, max)
> attributes  :
>          ID   COUNT
> CLASS_NAMES       RED     GREEN      BLUE OPACITY
>   from:   1 7128758                                  Open Water (Fresh)
> 0.3568627 0.4588235 0.6392157       1
>   to  : 253  427139 Southern and Central Appalachian Oak Forest - Xeric
> 0.5372549 0.6666667 0.3294118       1
>
>> #Open reclass table.  Three columns From/To Values for input range, new
> value for output
>> recls = read.csv(file="
> SecondReclassTable_Rinput.csv", head=FALSE,
> sep=",")
>> recls = as.matrix(recls)
>> recls
>         V1  V2 V3
>   [1,]   1   7  0
>   [2,]  10  12  1
>   [3,]  16  26  0
>   [4,]  30  33  6
>   [5,]  35  37  0
>   [6,]  38  60  6
>   [7,]  61  64  4
>   [8,]  66  68  6
>   [9,]  71  71  4
> [10,]  72  74  3
> [11,]  76  77  4
> [12,]  79  79  3
> [13,]  82  82  6
> [14,]  85  85  4
> [15,]  86  86  6
> [16,]  90  96  4
> [17,]  98  99  6
> [18,] 100 100  4
> [19,] 102 109  6
> [20,] 118 118  0
> [21,] 119 119  6
> [22,] 124 127  0
> [23,] 141 143  1
> [24,] 145 149  0
> [25,] 151 182  2
> [26,] 183 188  4
> [27,] 192 206  2
> [28,] 207 207  0
> [29,] 213 216  5
> [30,] 217 217  1
> [31,] 218 228  5
> [32,] 231 233  4
> [33,] 238 238  2
> [34,] 245 250  5
> [35,] 253 253  6
>
>
>> ecos = reclassify(testarea, recls)
>>
>> ecos
> class       : RasterLayer
> dimensions  : 34, 33, 1122  (nrow, ncol, ncell)
> resolution  : 30, 30  (x, y)
> extent      : 1200009, 1200999, 999992.1, 1001012  (xmin, xmax, ymin, ymax)
> coord. ref. : +proj=aea +lat_1=29.5 +lat_2=45.5 +lat_0=23 +lon_0=-96 +x_0=0
> +y_0=0 +ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs
> data source : in memory
> names       : layer
> values      : 0, 231  (min, max)
>
>