trying to create a loop that finds a value in an array and creates a matrix with it

I have an array TT where the first column is matlab serial date numbers and each other column is data for various variables.

I want to create a loop where the interation is

i = datenum(2018,1,1,00,00,00):0.208:datenum(2018,12,4,00,00,00)

0.208 is the difference between half hour periods in matlab serial date numbers. so i should loop through all the values in my first column. The problem is that these values are floating points. additionally, i'm not sure how to create a matrix with this. For more detail, what I want to do is create a matrix where for each i value, the matrix either has the corresponding variable data or if there is no value in TT that matches i, it'll insert an NaN into the matrix. I hope this makes sense. Any guidance would be appreciated.

[Andrei Bobrov]

Susan! Please attach example your data as mat-file.

[Stephen23]

"0.208 is the difference between half hour periods in matlab serial date numbers"

Almost. Serial date numbers count up in days, so one half hour has a value of

>> 1/24/2
ans =  0.020833

[Susan Santiago]

You said in a .mat file so I assume you mean my array. This is it. If this is not what you meant, please let me know. And yes thank, I miswrote. It should be 0.020833

Answer 1

[Walter Roberson]

If you have a new enough version then I recommend changing to timetable objects and using retime()

Otherwise consider using interp1() . If that is not suitable, then use ismembertol() to find matching items. If your system is too old to have ismembertol() then loop with testing ranges of values.

[Andrei Bobrov]

+1

[Susan Santiago]

I have the 2017 version. I'll look into ismembertol. Thanks