[R-sig-Geo] Selecting a range of longitude and latitudes

[Tom Philippi]

Trav--
Are you trying to specify a grid of each of those lon values by each of
those lat values?  cbind() is matching the first lon with the first lat,
the second with the second, generating a diagonal of locations.  [That's
also why there have to be as many lats as lons.]  To fill out the grid of
each lon with each lat, look at expand.grid(103:116, 3:16)

Tom

On Thu, Apr 18, 2019 at 6:51 PM rain1290--- via R-sig-Geo <
r-sig-geo using r-project.org> wrote:

> Hi Ben (and everyone),
>
> Ah, yes, you're right - using the suggestion that you specified, that
> error message disappeared! So, if I understand, this would take all of the
> grid cells within those specified longitude and latitude ranges (i.e. that
> entire area)?
> That said, when I try plotting this using the following:
> get <- ncvar_get(Model1, "cum_co2_emi-CanESM2")   #for x-axis (140 values)
> Model2 <- brick("MaxPrecCCCMACanESM21pctCO2.nc", var="onedaymax")    #for
> y-axis (140 values)
>
> Hope2 <- extract(Model2, lonlat)
>
> plot(get,Hope2, type="l",col="green", lwd="3", xlab="Cumulative emissions
> (TtC)", ylab="One-day maximum precipitation (mm/day)", main="CanESM2")
> I receive this error:
> Error in xy.coords(x, y, xlabel, ylabel, log) :
>   'x' and 'y' lengths differ
> *Note that I do not have this problem when specifying a "specific"
> longitude and latitude, rather than a range. Is there any reason for this?
> Thanks, again
> -----Original Message-----
> From: Ben Tupper <btupper using bigelow.org>
> To: rain1290 <rain1290 using aim.com>
> Cc: r-sig-geo <r-sig-geo using r-project.org>
> Sent: Thu, Apr 18, 2019 9:26 pm
> Subject: Re: [R-sig-Geo] Selecting a range of longitude and latitudes
>
> Hi,
> The example you give is different than the one listed in the error
> message.  In your example you bind two 14-element vectors into a matrix of
> two columns.
> cbind(103:116, 3:16)
> But in the error you show the first vector is only 8 elements long...
> cbind(103:110, 3:16)
> When R encounters an attempt to bind columns of unequal length it will try
> to "recycle" the shorter vector as long as it is a multiple of the longer.
> In this case of binding an 8-element vector and a 14-element vector it
> fails.
> Note that shortening up the first vector to 7 does work since 7 is a
> multiple of 14...
> cbind(103:109, 3:16)      [,1] [,2] [1,]  103    3 [2,]  104    4 [3,]
>  105    5 [4,]  106    6 [5,]  107    7 [6,]  108    8 [7,]  109    9 [8,]
>  103   10 [9,]  104   11[10,]  105   12[11,]  106   13[12,]  107   14[13,]
>  108   15[14,]  109   16
>
> Note how the sequence 103...109 appears twice in the first column.
> Recycling is nice (and handy) until you get surprised by it.
> Cheers,Ben
>
> On Apr 18, 2019, at 8:37 PM, rain1290--- via R-sig-Geo <
> r-sig-geo using r-project.org> wrote:
> Hi there,
> I am trying to specify a range of longitudes and latitudes. I tried this
> using the following:
>
>
> lonlat <- cbind(103:116, 3:16)  #This would specify a range of longitudes
> and latitudes
>
> However, I receive the following warning message:
> Warning message:
> In cbind(103:110, 3:16) :
>   number of rows of result is not a multiple of vector length (arg 1)
>
> When I specify the longitude and latitude of a specific location, though,
> it works just fine, like this:
> lonlat <- cbind(103, 3)
>
> Am I specifying the ranges of coordinates incorrectly? The warning message
> would suggest yes, but I do not understand why.
> Thanks, and any help with this would be greatly appreciated!
> ~Trav.~
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>
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>
> Ben Tupper
> Bigelow Laboratory for Ocean Sciences
> 60 Bigelow Drive, P.O. Box 380
> East Boothbay, Maine 04544
> http://www.bigelow.org
> Ecological Forecasting: https://eco.bigelow.org/
>
>
>
>
>
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