



 Hi,

 I'm trying to plot some data (z) that is linked to lat&long coordinates

 (x&y). These coordinates are not however on a regular grid. I also have some

 shapefiles on which I would like to overlay the data. I can plot the

 shapefiles (country/city outlines) and overplot the data, but only using

 quilt.plot because I otherwise always get the error message that

 'Error in image.default(..., add = add, col = col) :

    increasing 'x' and 'y' values expected'

 which has something to do with the organization of my data but I cannot

 figure out how to change it correctly. This is the code that I have that

 works:

 
 
 data<-read.csv('with coord_observational log data trends all years all

 data.8.11.10.csv', header=TRUE)

 
 ## this is what the 'data' looks like:

 head(data)

    X SiteCode Latitude   Longitude           p perc_per_year

 perc_per_year_lower

 1 1      A30 51.37357 -0.29172504 0.369164267    -0.4781589

 -1.390382

 2 2      BB1 51.68299 -0.03254972 0.005546354    -3.1810064

 -5.665312

 3 3      BG1 51.56375  0.17789100 0.000405606    -3.2260763

 -5.344999

 4 4      BG2 51.52939  0.13285700 0.434756172    -5.1558318

 -22.123800

 5 5      BH1 50.82334 -0.13724510 0.183375348    -0.8735160

 -2.240289

 6 6      BH2 50.82785 -0.17051300 0.002702969    -2.1443157

 -3.543378

    perc_per_year_upper         sig

 1           0.4786508 -999.000000

 2          -0.8588293   -3.181006

 3          -1.5251377   -3.226076

 4          11.0957982 -999.000000

 5           0.3431518 -999.000000

 6          -0.7966338   -2.144316

 
 #read in the shapefile

 england<-readShapePoly('D:/arcGIS/england boundary/england.shp')

 class(england)

 #define the projection

 proj4string(england)<-CRS('+proj=tmerc +lat_0=49 +lon_0=-2 +k=0.999601271625

 +x_0=400000 +y_0=-100000 +ellps=airy +units=m +no_defs')

 # transform the map into the WGS84 projection (epsg:4326):

 england.wgs<-spTransform(england, CRS('+init=epsg:4326'))

 
 plot(england.wgs)

 #plot data over the map:

 quilt.plot(data$Longitude, data$Latitude, data$perc_per_year, add=TRUE)

 
 My problem is that I would like to be able to change how this data looks

 (not just 'grid squares', but circles, etc) which I can't seem to do wtih

 quilt.plot. If I could do this I could plot one layer of gridded data

 (squares as in quilt.plot) and overlay a second layer of 'z' data as points.

 I have tried plot.surface and image.plot and a number of others, but because

 of the error message that I get above it won't work. I can use image.plot,

 etc if I create a grid and interpolate my data onto the grid (see code

 below), but I don't want interpolated data, I would like discreet values for

 each lat&long.

 
 
 x<-seq(-4,2, by=0.0625)

 y<-seq(50,53, by=0.0625)

 d1<-expand.grid(x=x, y=y)

 data.li<-interp(data$Longitude, data$Latitude, data$perc_per_year,

 duplicate='mean')


 So my questions are, (1) is there a different function that I should be

 using with my data as it is and still be able to overplot it onto the map

 that i've plotted? or (2) is there a way to create this grid and integrate

 my data into the grid, but not interpolate it?

 
 Any help would be very much appreciated. My R skills just are not good

 enough to do this yet.

 
 Thank you!!

 Erika.



 		 	   		  
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