插值數據

Question

讓我們假設我有一個3×5矩陣中R：

4 5 5 6 8 
3 4 4 5 6 
2 3 3 3 4 

我想在這些值之間進行內插在由25來創建尺寸15的矩陣I還要指定插值是線性的，高斯等。我該怎麼做？

舉例來說，如果我有這樣的

2 3 
1 3 

小矩陣，我希望它由3變成3，那麼它可能看起來像

2 2.5 3 
    1.5 2.2 3 
    1 2  3 

Answer 1

app <- function(x, n) approx(x, n=n)$y # Or whatever interpolation that you want 

apply(t(apply(x, 1, function(x) app(x, nc))), 2, function(x) app(x, nr)) 
    [,1] [,2] [,3] 
[1,] 2.0 2.50 3 
[2,] 1.5 2.25 3 
[3,] 1.0 2.00 3 

Answer 2

很久以前我寫了一個類似的玩具，除了我從未想過定義插值函數。還有raster::disaggregate。

zexpand<-function(inarray, fact=2, interp=FALSE, ...) { 
# do same analysis of fact to allow one or two values, fact >=1 required, etc. 
fact<-as.integer(round(fact)) 
switch(as.character(length(fact)), 
      '1' = xfact<-yfact<-fact, 
      '2'= {xfact<-fact[1]; yfact<-fact[2]}, 
      {xfact<-fact[1]; yfact<-fact[2];warning(' fact is too long. First two values used.')}) 
if (xfact < 1) { stop('fact[1] must be > 0') } 
if (yfact < 1) { stop('fact[2] must be > 0') } 
bigtmp <- matrix(rep(t(inarray), each=xfact), nrow(inarray), ncol(inarray)*xfact, byr=T) #does column expansion 
bigx <- t(matrix(rep((bigtmp),each=yfact),ncol(bigtmp),nrow(bigtmp)*yfact,byr=T)) 
# the interpolation would go here. Or use interp.loess on output (won't 
# handle complex data). Also, look at fields::Tps which probably does 
# a much better job anyway. Just do separately on Re and Im data 
return(invisible(bigx)) 
}