function [z] = zscore_mvpa(x,dim)

% This is a simple replacement for the Matlab Stats toolbox zscore % function. It differs ever so slightly, because it takes in an % optional DIM argument that determines which dimension it should % operate along (like MAX, MIN, SUM, MEAN etc.). % % Note: if you’re looking for an MVPA function to zscore your % patterns as part of the subj structure, see ZSCORE_RUNS.M - this % is just a simple auxiliary function to stand in for ZSCORE.M % % DIM (optional, default = 1 for matrices or column vectors, 2 for row % vectors). These defaults are ever so slightly different than % those of the Stats toolbox ZSCORE.M - here, the default dim is 1 % for matrices (2D max), whereas the Stats toolbox can deal with ND % matrices and will use the lowest dimension with more than 1 value % in it % % Note: this has been tested, but perhaps not as carefully as it % should be

% This is part of the Princeton MVPA toolbox, released under the % GPL. See http://www.csbmb.princeton.edu/mvpa for more % information.

if ~isnumeric(x) error(‘Can”t zscore non-numeric data’); end

if isempty(x) z = []; return end

% If you don’t get fed a dim: % if it’s a row vector, dim = 2. if it’s a column vector, dim = 1 % else, it must be a matrix, so default to 1 if ~exist(‘dim’,’var’) dim = 1; if isrow(x)==1 dim = 2; end end

switch(dim) case 1 z = do_z(x); case 2 z = do_z(x’)’; otherwise error(‘Can only manage up to 2D matrices’); end

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% function [z] = do_z(x)

nVals = size(x,1); warn = warning(‘off’,’MATLAB:divideByZero’); xbar = repmat(mean(x),[nVals 1]); sd = repmat(std(x),[nVals 1]); warning(warn) sd(sd==0) = 1; z = (x - xbar) ./ sd;



Home - Blog - Startups - Software - Research - Writing

Email me - updated 31 Dec 2012