如何计算R中点组的质心？

Question

In Python, you could have eg a list of lists like lst = [[0, 1, 2], [2, 3, 4]] .

To calculate the centroid in this, you could have the following code:

n = len(lst[0])
centroid = [0]*n

def centroid(*args):
    for i in range(n):
        _sum = sum([element[i] for element in lst])
        centroid[i] = _sum/len(lst)
    return centroid

get_centroid(lst)

How can I do the same thing in R for a group of points generally? Ie how can the same function be created?

Answer 1

It seems like they calculate the centroid coordinate-wise as the mean over the corresponding dimension, hence

lst <- list(c(0, 1, 2),c(2, 3, 4))

calcCentroid <- function(pointList) {
  rowMeans(do.call("cbind",pointList))
}

calcCentroid(lst)

should do the work. I assume you have the points in a list and every point has the same length . Then, you can combine them all together to a numeric matrix. Its columns contain the points. Then you can perform a rowwise mean, which in R can be done via rowMeans , which is a highly optimized function just for this job.