If loop to find date where values are bigger than certain threshold

Question

I am struggling with my Matlab homework.

I have a datetime array called "date" and two arrays (X and Y) of the type double containing measurements for each time step.

I have to do the following task:

Select all time steps where both X AND Y are larger than their respective Z value. Store the dates of these time steps in a new variable. Name it 'C'

Z and Y are 52584x1 double vectors and date is a vector of the format 52584x1 datetime (dd.MM.yyyy hh:mm)

I tried:

%Some Dummy Data:
Y = 1:8:80
X = 2:4:40
t1 = datetime(2013,11,1,8,0,0)
t2 = datetime(2013,11,10,8,0,0)
date = t1:t2

Z = 8;

for i = length(date) 
    if X(i) > Z && Y(i) > Z
         C=date(i)
    end
end

I guess something is wrong with C=date(i)

Thankful for any help!

Answer 1

I guess what you need might be something like below:

Z = 8;
for i = 1:length(date) 
    if X(i) > Z && Y(i) > Z
         C(end+1)= date(i);
    end
end

alternative : C = date((X>Z)& (Y>Z)) or C = date(min([X;Y],[],1) > Z) is a more efficient solution instead of using for loop