Graphics Programs Reference
In-Depth Information
fid = fopen('asc.dat');
The
fopen
command returns a
file identifier
,
fid
, which is an integer
that must be used as the first argument of any subsequent file-reading
or file-writing function that uses the file
asc.dat
. If the file cannot be
opened (for example, if it does not exist or exists in a directory that
cannot be found by matlab), then a value
fid=-1
is returned. Once
the file is opened the data can be read using the following command:
>> a = fscanf(fid,'%d/%d %d:%d:%d %g%g%g%g%g%g');
>> size(a)
ans =
55
1
The
fscanf
command has read in all the data up to the end of the file.
In the file are 11 numbers per line (2 numbers in the date, plus 3 in the
time, plus 6 other numbers), and there are 5 lines, for a total of 55 data
values; these have been read into a column-vector called
a
. The format
string '
%d/%d %d:%d:%d %g%g%g%g%g%g
' means “look for two decimal
numbers separated by slashes, skip some whitespace, then look for three
decimal numbers separated by colons, skip some more whitespace, then
look for six general format floating point numbers” (see the section on
string conversion on page 79).
fscanf
reads in such numbers until the
end of the file, or you can put in a parameter to read in a certain number
of values. We only now need to reshape the vector
a
to a matrix having
11 columns
N = length(a)/11;
a = reshape(a,11,N)';
The date and time values are in the first five columns:
>> a(:,1:5)
ans =
10
6
11
18
0
10
6
11
18
1
10
6
11
18
2
10
6
11
18
3
10
6
11
18
4
And the remaining values are
>> a(:,6:11)
ans =
-34.8550 151.3057 216.4000
70.9100 -61.2300
0.2900
-34.8555 151.3065 214.8000
71.3800 -60.8000
-0.8800
-34.8561 151.3073 212.7000
71.8600 -60.6400
-1.6400
-34.8566 151.3081 210.8000
72.4000 -60.3500
-1.6700
-34.8572 151.3089 209.7000
72.8300 -60.0600
-1.3300
