How can you change effect in Nivo Slider based off of previous or next slide keypress?

Question

I want to change the transition effect on Nivo Slider based off of which button was pressed. Any ideas of how to accomplish this?

Update To clarify

Answer 1

Add this to "jquery.nivo.slider.js" before comment "// Run effects" after comment and code in "// Custom transition as defined by "data-transition" attribute". This show change current effect if you click on left or right arrow or buttons. For this work you must have imageis in HTML without "data-transition" attribute and default effect you must define in "jquery.nivo.slider.js" under comment "//Default settings" because "data-transition" attribute is prefer. I code it right know for my project.

        if(nudge === 'prev'){
            currentEffect = 'slideInLeft';
        } 
        else if (nudge === 'next'){
            currentEffect = 'slideInRight';
        }
        else if (nudge === 'control'){
            currentEffect = 'fade'; /*test*/
        }