indicator that plots the sum of 2 indicators

 
i am having problems with calling indicators from another indicator.Can anyone help me with coding an indicator that plots the difference or sum of two indicators.i wish to use one indicator ,the first indicator will be running with period 13 and another with period 21.their sum or difference is what i am interested in.will be grateful.
 
thezim: i am having problems ... will be grateful.
  1. You have only three choices: Search for it, learn to code it, or pay someone. We're not going to code it FOR you. We are willing to HELP you when you post your attempt (using SRC) and the nature of your problem.
  2. "Having problems" is meaningless - just like saying the car doesn't work. Doesn't start, won't go in gear, no electrical, missing the key, flat tires - meaningless. There are no mind readers here.
  3. Ever hear of the MACD? Do you know what it is? Did you try to look at its code? How grateful? See previous choice.
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