Query regarding timeseries.js in app modile

Hey Guys, I am a student and trying to develop an app using app template. I am facing problem related to timeseries.js library. Whenever I try to append value using append function , I get the following error.

" timeseries.append datastore[valve_position_1] is undefined " .

valve position 1 is already configured in config.app and it is being updated when ever I change the feed value.

can smeone help me in solving this error. I already checked timeseries.js library and couldn’t figure out the problem.

I am using mysolarpv.php as a reference.