找n个点相距最远的k个

</pre><pre name="code" class="html">getTargetPoint <- function(data, k, method = 'euclidean'){
    
	#找第i个最远的点
	#n,点的个数，即为distMatrix行数
	getPos <- function(pos, distMatrix, n){
	
	    #得到第i个点离选出的点的距离最小值
		i <- length(pos) + 1
	    getMinDist <- function(pos, distMatrix, i){
		    min <- distMatrix[pos[1], i]
		    for(a in pos){
			    if(min > distMatrix[a, i]){
				    min <- distMatrix[a, i]
				}
			}
			return(min)
		}
		
	    #距离最小值最大
		p <- 0
		max <- 0
	    for(a in 3:n){
			minDist <- getMinDist(pos, distMatrix, a)
			if(max < minDist){
			    max <- minDist
				p <- a
			}
		}
		
		return(p)
	}
	
    data <- as.matrix(data)
    size <- dim(data)
    if(k<2 | k>size[1]){
	    return(matrix())
	}
	distMatrix <- as.matrix(dist(data, method, upper = T, diag = T))
	
	#先找两个最远的点
	maxDist <- distMatrix[2, 1]
	pos <- c(0, 0)
	for(i in 2:size[1]){
	    for(j in 1:(i-1)){
		    if(maxDist < distMatrix[i, j]){
			    maxDist <- distMatrix[i, j]
				pos[1] <- i
				pos[2] <- j
			}
		}
	}
	result <- matrix(rep(0, size[2] * k), nrow = k)
	result[1, ] <- data[pos[1], ]
	result[2, ] <- data[pos[2], ]
	
	if(k==2){
	    return(result)
	}
	
	#找剩下的k-2个点
	for(i in 3:k){
	    pos[k] <- getPos(pos, distMatrix, size[1])
	    result[i, ] <- data[pos[k], ]
	}
	
	return(result)
}

data <- matrix(data = c(1,2,3,4,5,5,7,8), nrow = 4)
getTargetPoint(data = data, k = 3)

#结果
#> getTargetPoint(data = data, k = 3)
#       [,1] [,2]
#[1,]    4    8
#[2,]    1    5
#[3,]    3    7