graph twoway line: How to create a condition (if for example prices are the same for two lines)?

[Michael Duarte Goncalves]

Hi everyone,

I would like to create a graph in which, when the two prices are identical, the green colour must prevail over the red colour (i.e. on the graph, when the two values are identical, the green colour must appear).

I enclosed the graph. What I want is that green line should the only one to be viewed from 01 July 2021 to 15 June 2022 (where both lines coincide). Again for approximately on the 1 January 2023 onwards.
In-between, the two lines should be on the graph, as their prices are not the same.

Original graph:

dataex:

* Example generated by -dataex-. For more info, type help dataex
clear
input double Date float(CompetitivePrice CompetitivePrice_noInter day_Date month_Date year_Date)
22462 110.08 110.08  1 7 2021
22463 110.58 110.58  2 7 2021
22464 102.26 102.26  3 7 2021
22465  88.82  88.82  4 7 2021
22466 106.42 106.42  5 7 2021
22467 105.88 105.88  6 7 2021
22468 107.03 107.03  7 7 2021
22469 101.45 101.45  8 7 2021
22470 104.71 104.71  9 7 2021
22471 107.55 107.55 10 7 2021
end
format %td Date

I tried something, but it gave me a weird graph:

gen SamePrice = (CompetitivePrice == CompetitivePrice_noInter)
# delimit;

twoway (line CompetitivePrice Date if SamePrice, lcolor(green))
       (line CompetitivePrice Date if !SamePrice, lcolor(red)),
       legend(cols(1) label(1 "Factual") label(2 "No Intervention Scenario")
                      label(3 "Long Intervention Scenario") position(12) ring(0))
       xlabel(, angle(45))
       ylabel(0(100)800)
       tlabel(01jul2021 01oct2021 01jan2022 01apr2022 01jul2022 01oct2022 01jan2023 01apr2023 31jul2023)
       xtitle("Date") ytitle("€/MWh")
       plotregion(margin(none))
       ;
# delimit cr

Attempted graph with above code:

Could you please tell me how to do this?
Thanks in advance.

Michael

[Maarten Buis]

If you plot multiple graphs with twoway this first graph will be drawn first, the second on top of that, the third on top of that, etc. So if you want the green curve to be on top if the green and red curve are the same, you just specify it last. No need for if conditions.

[Nick Cox]

Red and green should never be juxtaposed or superimposed in any case, as difficulty in distinguishing red and green is one of the most kinds of so-called colour blindness. See e.g. https://venngage.com/blog/color-blind-friendly-palette/

Red and blue or orange and blue often work well together.

[Michael Duarte Goncalves]

Good morning Maarten Buis,
Good morning Nick Cox,

Thank you very much for your answers!

I tried #2 and it works perfectly well. Thank you!
#3: Thank you for your feedback! You are right, I will change that.

Lovely morning to both of you.
Best,

Michael