# mvpa2.measures.rsa.squareform¶

`mvpa2.measures.rsa.``squareform`(X, force='no', checks=True)

Converts a vector-form distance vector to a square-form distance matrix, and vice-versa.

Parameters: X : ndarray Either a condensed or redundant distance matrix. force : str, optional As with MATLAB(TM), if force is equal to ‘tovector’ or ‘tomatrix’, the input will be treated as a distance matrix or distance vector respectively. checks : bool, optional If `checks` is set to False, no checks will be made for matrix symmetry nor zero diagonals. This is useful if it is known that `X - X.T1` is small and `diag(X)` is close to zero. These values are ignored any way so they do not disrupt the squareform transformation. Y : ndarray If a condensed distance matrix is passed, a redundant one is returned, or if a redundant one is passed, a condensed distance matrix is returned.

Notes

1. v = squareform(X)

Given a square d-by-d symmetric distance matrix X, `v=squareform(X)` returns a `d * (d-1) / 2` (or `\${n choose 2}\$`) sized vector v.

v[{n choose 2}-{n-i choose 2} + (j-i-1)] is the distance between points i and j. If X is non-square or asymmetric, an error is returned.
1. X = squareform(v)
Given a d*(d-1)/2 sized v for some integer d>=2 encoding distances as described, X=squareform(v) returns a d by d distance matrix X. The X[i, j] and X[j, i] values are set to v[{n choose 2}-{n-i choose 2} + (j-i-1)] and all diagonal elements are zero.