Change of data format

Hello,

I have a *.txt file with data in the following format (say, file1):

00Z01JAN1948 0.00579036

06Z01JAN1948 0.00346197

12Z01JAN1948 0.00728858

18Z01JAN1948 0.0145886

00Z02JAN1948 0.00592358

06Z02JAN1948 0.00298858

12Z02JAN1948 0.00788106

18Z02JAN1948 0.0123543

00Z03JAN1948 0.0219563

06Z03JAN1948 0.023932 (and so on up to 2014...)

So, the first column contains hour (first two values), (Z stands for zullu time, I don't need that) and the rest is date. The second column contains some data (pressure gradients).

The second file (say, file2) contains dates in the format:

1011949 0 %(this would be Jan 1st, 1949 at 00 h)

1011949 6 %(this would be Jan 1st, 1949 at 06 h)

1011949 12

1011949 18

2011949 0 %(this would be Jan 2nd, 1949 at 0 h)

2011949 6 (and so on until 2010)

file1 and file2 are not the same in size; file1 is longer and has all dates from 1948 to 2014 while file2 has some of dates from 1949 to 2010.

I need to extract pressure gradient valus from file1, but only for the dates (and hours) given in file2. So it would be like this: 1011949 0 pressure gradinet value for that date

1011949 6 pressure gradinet value for that date

1011949 12 pressure gradinet value for that date

1011949 18 pressure gradient value for that date

Please, could you help me with this? I am not sure how to transfer dates from one format to other so that I compare two sets of data.

Thanks, Djordje

Answer 1

[dpb]

Read the two files and convert to Matlab datenum datenums...

00Z01JAN1948 0.00579036

Format for first would be

fmt1='%s %f';
c=textscan(fid,fmt1);

The 'Z' adds a minor complication -- you can approach one of two ways; probably as simple as any is to simply replace it in place in the call...

dn=datenum(strrep(c(1),'Z',''),'hhddmmmyyyy');
dn =
 1.0e+05 *
  7.1149
  7.1149
  7.1149
>> datestr(ans)
ans =
01-Jan-1948 00:00:00
01-Jan-1948 06:00:00
01-Jan-1948 12:00:00
>>

The second is similar except the date format string uses only the one/two character for the day so

dn2=datenum(c2(1),'dmmyyyy');

Then for the values from the first file in the second,

pselect=c{2}(ismember(dn2,dn);

[per isakson]

pselect=c{2}(ismember(dn2,dn); &nbsp Is that robust when dn includes hour values not equal to zero?

[djr]

I've modified dn2 to have all hours so it works fine. Otherwise, it would read data at 00 hour only.

[dpb]

woopsies...concentrated on fixup of the dmy field and forgot the rest -- good catch. --dpb

Answer 2

[djr]

Thank you very much.