You are taking wrong parameter for series2[i].
series[i] = separate(series[i]); //separate first digit
series2[i] = separate2(series[i]); // separate second digit
Should be
series[i]...
Type: Posts; User: John Joe
You are taking wrong parameter for series2[i].
series[i] = separate(series[i]); //separate first digit
series2[i] = separate2(series[i]); // separate second digit
Should be
series[i]...