get_trials_params.m

function [vDirection,vWg,vTask, vOnset] = get_trials_params(params)
% GET_TRIALS_PARAMS this function randomizes the direction (CW/CCW)
% and presence of stimuli, the order of the detection and discrimination
% blocks, and the timing of events.

Nsets = params.Nsets;
Nblocks = params.Nblocks;

% randomize blocks for detection/discrimination. Always interleaved, but
% the first can be detection or discrimination.
% 0 is discrimination, 1 detection
vTask = reshape([ones(Nblocks/2,1) zeros(Nblocks/2,1)]',Nblocks,1);
if binornd(1,0.5)
    vTask = 1-vTask;
end

%initialize
[vDirection, vWg] = deal([]);

% loop over experimental blocks
for i=1:length(vTask)
    
    % is this a detection or a discrimination block?
    detection = vTask(i);
    % create all four types of events: CW_present, CW_absent, CCW_present
    % and CCW_absent. (first column: Wg, second column: direction).
    block_array = [ones(params.trialsPerBlock/4,1) ones(params.trialsPerBlock/4,1); ...
        zeros(params.trialsPerBlock/4,1) ones(params.trialsPerBlock/4,1);...
        ones(params.trialsPerBlock/4,1) 3*ones(params.trialsPerBlock/4,1); ...
        zeros(params.trialsPerBlock/4,1) 3*ones(params.trialsPerBlock/4,1)];
    % if this is a discrimination block, all trials should be 'present'
    if ~detection
        block_array(:,1)=1;
    end
    
    %% randomize
    block_array = block_array(randperm(params.trialsPerBlock),:);
    vWg = [vWg; block_array(:,1)];
    vDirection = [vDirection; block_array(:,2)];
end

%% Randomize event timing

% the trial duration includes extra 0.8 seconds to make the minimum spacing
% between consecutive trials 800 milliseconds.
trial_duration = params.fixation_time + params.display_time...
    + params.time_to_respond + params.time_to_conf+0.8;
% this is the duration (in seconds) of all trials combined + 10 seconds 
% for the beginning of each experimental block.
used_time = trial_duration*length(vWg)+10*length(vTask);
% this is the duration (in seconds) of rest time that can be fiddled with.
spare_time = params.run_duration-used_time;
% to add gitter to all events, first I draw numbers from a uniform
% distribution between 1 and 0, and scale them so that the minimum is 0 and
% the maximum is 1.
gitter_vec = Scale(rand(size(vWg)));
% I then multiply them by the factor needed to make their total duration
% equal to the spare_time. 
gitter_vec = gitter_vec/sum(gitter_vec)*spare_time;
% add the trial duration and the instruction screens to the gitter_vec.
gitter_vec = gitter_vec+trial_duration;
gitter_vec = [0; gitter_vec];
gitter_vec(1:Nsets/Nblocks:end) = gitter_vec(1:Nsets/Nblocks:end)+10;
% now the vector of trial onsets is the serial accumulation of the gitter vec.
vOnset = cumsum(gitter_vec(1:end-1));

if vOnset(end)-params.run_duration > eps && ~params.calibration
    error('the randomization procedure went wrong')
end
end