MATLAB: I get “Unexpected Matlab expression”

unexpected matlab expression

function [Drcode, timer, lat, lon, u, v] = read_drifter_1('cc1.dat' , '0');
%


% usage [Drcode, timer, lat, lon, u, v] = read_drifter_1(filename, plotflag)
% this routine reads the data from the .dat files produced by the Android
% Drifter application, and provides the data.
%
fid = fopen('cc1.dat');
A = fgetl(fid);
timer=[];
lat=[];
lon=[];
u = [];
v = [];
while ~feof(fid),
    A = fgetl(fid);
    s = findstr(A,'  ');
    N = length(s);
    Rlat = str2num(A(s(1)+1:s(2)-1));
    Rlon = str2num(A(s(2)+1:s(3)-1));
    Ryy = str2num(A(s(5)+1:s(6)-1));
    Rmm = str2num(A(s(6)+1:s(7)-1));
    Rdd = str2num(A(s(7)+1:s(8)-1));
    Rhh = str2num(A(s(8)+1:s(9)-1));
    Rmin = str2num(A(s(9)+1:s(10)-1));
    Rsec = str2num(A(s(10)+1:length(A)));
    Rtime = datenum(Ryy, Rmm, Rdd, Rhh, Rmin, Rsec);
    lat = [lat; Rlat];
    lon = [lon; Rlon];
    timer = [timer; Rtime];
end
%
% Start a quality control regarding times
% Sort the data in increasing time
[timer2, Itime] = sort(timer,'ascend');
lat2 = lat(Itime);
lon2 = lon(Itime);
% remove the data taken at exactly the same time (double records)
dt = diff(timer2);
J = find(dt > 0);
timer = timer2(J+1);
lat = lat2(J+1);
lon = lon2(J+1);
% %
fclose(fid);
Drcode = [];
if plotflag ~=0, 
   figure
   plot(lon2, lat2,'.')
   hold on
   plot(lon, lat, 'o')
end
return
Christos

Best Answer

It looks like you haven't really understood how to define functions and how to use them.
The signature of a function is
function [outputvar1, outputvar2, ...] = functionname(inputvar1, inputvar2, ...)
where outputvarx and inputvarx are variable names that you then use in the body of your function. They must be variable names, you can't replace these by actual value. Strangely enough you've got it right in the function documentation. Your function signature should be
function [Drcode, timer, lat, lon, u, v] = read_drifter_1(filename, plotflag)
When you want to use that function, you don't go and edit that signature and write the values to use in there. Instead you call that function from the command line, a script, or another function. For example, if you want to use that function with the inputs 'cc1.dat' and 0, you'll call it with the line:
read_drifter_1('cc1.dat' , 0)
or if you want to see the outputs:
[somename, someothername, anothername, outputforlon, outputforu, outputforv] = read_drifter_1('cc1.dat' , 0)
Some other notes:
  • It's not an error but the return at the end of the function is unnecessary. Remove it.
  • The value you pass for plotflag should be logical or numerical, not a char array. You're meant to pass either true, false, 0, or 1, but not '0' or '1'. Both '0' and '1' would have the same effect as if you've passed true.
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