change selected radio jquery
Say you had radio buttons like these, for example:
<input type='radio' name='gender' value='Male'>
<input type='radio' name='gender' value='Female'>
  
And you wanted to check the one with a value of "Male" onload if no radio is 
checked:
$(function() {
    var $radios = $('input:radio[name=gender]');
    if($radios.is(':checked') === false) {
        $radios.filter('[value=Male]').prop('checked', true);
    }
});
