No Plot in the Chart

When I have this piece of code, it plots on the chart,

Buy = O>MA(C,20); ; 

Sell = O<MA(C,20);

but when I add more to it, like this, `Buy = O>MA(C,20) OR O>MA(C,8);

Sell = O<MA(C,20)-1;

The -1 in second line caused the problem with plotting. Can anyone tell me why?

@Veasnar, you will have to think about your logic here a bit more.

Your Sell Condition should evaluate to a True or False.

Your Sell is trying to do subtraction from a Logic value, so you will get an error.

Your Buy condition is TWO logical tests that are "OR"ed together. That is a Logical OR so it is allowed.

Not sure what you are after with the "-1" in the Sell, so you will have to define it better, and see if you can come up with a condition expression.

Thanks for your response, Snoopy.pa30,
"-1" is for yesterday or one day after it happened.

BTW, there is no error with compilation.

@Veasnar of course there is no error with compilation. You entered a mathematical equation. What you need is to familiar with the Ref function to refer to yesterday (or previous bar's)
http://www.amibroker.com/guide/afl/ref.html

If you are uncertain about what your calculations are creating then create an Exploration and see what all your variables are doing.

But also even though you have been a member of the forum for 10 months, you do not appear to have gone through some important steps in learning afl. I suggest you spend some significant time reading and coding what you find as you work your way through the resources listed in this forum post,

http://forum.amibroker.com/t/how-do-i-learn-afl/102/2

Good luck!

Thanks for your advice and suggestion, portfoliobuilder.