Finding threshold of matrix

Suppose u have a matrix A with rand (i.e 0-1). Now a threshold(x) of A is to be determined so that 70% of values of the given matrix A are greater than the threshold(x).

Answer 1

[Walter Roberson]

sort() and index 3/10 of the way through.

[MSP]

would that be faster than doing percentile

[Walter Roberson]

Yes. See the Algorithms section of https://www.mathworks.com/help/stats/prctile.html#btgyzpd-1 which describes the algorithm prctile uses.