how to plot current days open minus the prior days close?

[bmoney]

I am VERY green to coding and am struggling to figure out how to get thinkscript to use a close value from a previous period. I want to calculate after hours gap values by using the absvalue (open-priordayclose) but cant seem to figure out how to do that. any help is appreciated very much. thank you!

 

[mashume]

Assuming you're working on a day chart, this should get you going:

declare lower;

plot data = open - close[1];
plot zero = 0;

We can use the bracket notation to reference previous candles, so that [1] indicates "1 bar ago". There is an implicit [0] with the open as I used it. That is, if you don't put a number in brackets, it automatically assumes the last candle:

open == open[0]

and

close == close[0]

You can reference future bars using negative numbers, but be aware that this is the largest single culprit for repainting studies and un-produceable results in backtests. It has uses, but just be careful that [1] is one bar ago and [-1] is one bar from now.

happy trading,
mashume