# if condition picking certain day of week

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Dharma Khatiwada on 3 Aug 2022
Hi,
I am using a for loop using time as a variable. For day 1 (Monday) there is a value. Then I start a for loop starting from 4th day (Thursday). I want to use for loop only on Day 1(Monday) and Day 4 (Thursday) of every week for 40 weeks. This is related to a situation in radiation treatment where the radiation is given every Monday and Thursday.
I am using following script for 'for loop' which is obviously not true for my above situation. Any help will be appreciated.
Thanks
Dharma
syms x t
c2(x) = 2*dirac(x-1);%day 1
for j=4:4:40 %needs some modification
c2(x) = c2(x)+2*dirac(x-j);
end

KSSV on 3 Aug 2022
thedates = (datetime(2022,01,1):datetime(2022,1,31))';
d = day(thedates,'name') ;
idx = ismember(d,{'Monday','Thursday'}) ;
d(idx)
ans = 9×1 cell array
{'Monday' } {'Thursday'} {'Monday' } {'Thursday'} {'Monday' } {'Thursday'} {'Monday' } {'Thursday'} {'Monday' }
find(idx)
ans = 9×1
3 6 10 13 17 20 24 27 31
Dharma Khatiwada on 4 Aug 2022
Thank you KSSV,
As a beginner, I am still having difficulty to implement your idea in my code.
Could you help me to clarify further?
How do I use idx in place of j of following code? I want to see the j picking mondays, thursdays as a number and the maximum I want to go is upto 40 times. For example, if I count from tomorrow (thursday) as 1 then coming monday (second),..........upto 40 i.e. a total of 40 Monday plus Thursday.
syms x t
c2(x) = 2*dirac(x-1);%day 1
for j=4:4:40 %needs some modification
c2(x) = c2(x)+2*dirac(x-j);
end