How do I import a timestamp from an ASCII File?

Good Evening,

I am trying to calculate the difference in phase% (one of the columns in the documents that I attached) between two sensors -- Sensor 1 and Sensor 2. The main problem is that each sensor begins recording at a different time point. Luckily, they have timestamps. I am interested in utilizing these timestamps to "line up" the data to subtract the correct number from Sensor 2 at the same specific point in time from Sensor 1. Eg. (12:30:00 Sensor 1 Phase% Value) - (12:30:00 Sensor 2 Phase% Value).

I have been very successful using the Import Wizard and I can manipulate the data but the time column is converted into a string leaving the same, very small decimal in each cell. How do I indicate to the Import Wizard that the timestamp should be a different format or is there a simple way to manipulate the code to import the data as a time (hh:mm:ss)? I have attached .txt files instead of the original ASCII files and I have also attached the .m file that the import wizard has generated.

Thanks! Brittany

Answer 1

[dpb]

I don't use importdata; I'd recommend just reading the data files. Then convert the datestrings to internal *datenum*s and then you can do any selection/alignment/whatever using the datenum values (as well as plotting versus actual time).

fid=fopen('sensor1.txt');
data=textscan(fid,fmt,'headerlines',39,'collectoutput',true,'delimiter',';');
dn=datenum([char(data{1,1}(1:10,1)) char(data{1,1}(1:10,2))],'mm/dd/yyyyHH:MM:SS AM');
fid=fclose(fid);

NB: the concatenation of the cell strings in the first cell which contains a 2-column cell array of the date and time. Change the (1:10, ) reference to just show the first 10 rows to (:, ) with the first/second column as the second subscript as shown to get the full data array.

>> datestr(dn)
ans =
09-Apr-2014 17:36:34
09-Apr-2014 17:36:35
09-Apr-2014 17:36:36
09-Apr-2014 17:36:37
09-Apr-2014 17:36:38
09-Apr-2014 17:36:39
09-Apr-2014 17:36:40
09-Apr-2014 17:36:41
09-Apr-2014 17:36:42
09-Apr-2014 17:36:43

doc datenum   % and friends
doc datetick  % when you get ready for plotting...