matrix_singleSelect.js

var previousAnswer ="";

Qualtrics.SurveyEngine.addOnload(function() {
	var questionId = this.questionId;
	this.questionclick = function(event, element) {
		if (element.type == 'radio') {
			var options = document.querySelectorAll('.q-checked');
			for (var i = 0; i < options.length; i++) {
				var ansArr = options[i].htmlFor.split('~');
				var ansStr = ansArr[2] + '_' + ansArr[3];
				if (ansStr !== previousAnswer) {
					previousAnswer = ansStr;
					uncheckAllExcept(questionId, [ansArr[2], ansArr[3]]);
					break;
				}
			}
		}
	}
});

function uncheckAllExcept(questionId, chosen) {
	for (var i = 1; i < 4; i++) {
		for (var j = 1; j < 4; j++) {
			Qualtrics.SurveyEngine.registry[questionId].setChoiceValue(i,j, false);
		}
	}
	Qualtrics.SurveyEngine.registry[questionId].setChoiceValue(chosen[0], chosen[1], true);
}