How to multiply with a factor with time series data

I have to compute S by applying following formula = S = 1000/CN -10; where S and CN are daily time series data. By applying this script, matlab is only computing the first value correctly, whereas all other values I am getting -10 answer that is not correct. CN is 68, 78, 90, 90 , 78 etc for the days in the year.

Could you please suggest me code for this?

Answer 1

[Thorsten]

 CN = [68, 78, 90, 90, 78];
 S = 1000./CN - 10;