[R] Using image/contour with unevenly spaced data...

[David Winsemius]

On Nov 18, 2010, at 10:52 PM, Jason Rupert wrote:

> Is it possible to plot unevenly spaced data with image/contour  
> function?
>
> Below is an example of the type uneven data that I'm trying to plot  
> with
> image/contour functions.  For example, I would like to have the x- 
> distance on
> the x-axis and y-distance on the y-axis and then the temperature  
> values
> determine the color used.  Unfortunately this data was sampled such  
> that it is
> not evenly spaced on a Cartesian plot.
>
> I was hoping that image(temp_samples) or contour(temp_samples) or  
> something
> similar would work, but my attempts didn't succeed.
>
> Thanks for any feedback insights and hints...
>
> hyp_distance<-seq(1,15)
> angle_deg_val<-seq(0,15)
>
>
> x_distance_val<-NULL
> y_distance_val<-NULL
>
> for(ii in 1:length(hyp_distance))
> {
>        for(jj in 1:length(angle_deg_val))
>        {
>                x_distance_tmp<- 
> hyp_distance[ii]*cos(angle_deg_val[jj]*pi/180)
>                y_distance_tmp<- 
> hyp_distance[ii]*sin(angle_deg_val[jj]*pi/180)
>
>                x_distance_val<-c(x_distance_val, x_distance_tmp)
>                y_distance_val<-c(y_distance_val, y_distance_tmp)
>        }
> }
>
> temperature_vals<-rnorm(length(x_distance_val), 75, 2.2)
>
> temp_samples<-cbind(x_distance_val, y_distance_val, temperature_vals)

library(akima)
ak.fan <- interp(temp_samples[,1],temp_samples[,2],temp_samples[,3] )
  contour(ak.fan)

-- 
David Winsemius, MD
West Hartford, CT