Hello, good afternoon
I have two data variables as below:
data is a matrix 150x2
centroids is a matrix 3x2
Im trying to execute broadcast like in python, and get a vector x, y to get subtracted from all 150x2 observations in data. How to perform this calculation?
data .- centroids[1, :]
Use data .- centroids[1, :]' to transpose centroids[1,:] to a 1 \times 2 row vector.
See also Unintuitive Julia result: selecting a row from a matrix
When you index an axis with a number, the result removes that axis, so you went from a 3x2 matrix to a 2-length vector. Broadcasting lines up to the leftmost axis not the rightmost, so 15x2 is incompatible with 2. Besides using a transpose to get a 1x2 matrix, you can actually keep the axis in the first place, you just have to index with a 1-length range instead of a number centroids[1:1, :].
Thank you guys for the help. I’m trying to port a kmeans algorithm from python to julia, and found that difference from numpy and julia. I will try the solutions and soon will return in this post.
It’s a bit confusing going between, it’s rooted in how C is row-major and Julia is column-major but they both try to adhere to conventional matrix notation. If it helps, here’s some pointers:
