Error using imwrite()

I'm getting an error in my function when using the imwrite() command. The error states:

Error using wgifc
Can only append to GIF89a format GIFs.

Error in writegif (line 306)
wgifc(mat, map, filename,writemode,disposalmethod,delaytime,...

Error in imwrite (line 559)
        feval(fmt_s.write, data, map, filename, paramPairs{:});

Error in animateBird (line 127)
            imwrite(imind,cm,filename,'gif','WriteMode','append');

Error in PlotRun3 (line 8)
animateBird('allPoints.mat', 1,'xy.gif')

Last week, there was no issue and I have not modified the code. Any help would be appreciated!

%% Import data
% imported .csv file
set(0,'DefaultLegendAutoUpdate','off');
load(dataMatrix);

%% Plot data on 3D plot
animPlot = figure(1);
hold on
% Right Wing
plot3(allPoints(18:300,1),... %x
      allPoints(18:300,2),... %y
      allPoints(18:300,3));   %z
% Left Wing
plot3(allPoints([1:138,142:164,171:191,196:222,225:267,285,288:293],4),...  %x
      allPoints([1:138,142:164,171:191,196:222,225:267,285,288:293],5),...  %y
      allPoints([1:138,142:164,171:191,196:222,225:267,285,288:293],6));    %z
% Beak
plot3(allPoints([66:263,278:292],7),...   %x
      allPoints([66:263,278:292],8),...   %y
      allPoints([66:263,278:292],9));     %z
% Left Tail
plot3(allPoints([51:65,72:256],10),...   %x
      allPoints([51:65,72:256],11),...   %y
      allPoints([51:65,72:256],12));     %z
% Right Tail
plot3(allPoints(47:259,13),...          %x
      allPoints(47:259,14),...          %y
      allPoints(47:259,15));            %z

grid on

% Select axis
if selection == 1
    view(0,90)  % XY
elseif selection == 2
    view(0,0)   % XZ
elseif selection == 3
    view(90,0)  % YZ
elseif selection == 4
    view(-135,30)
end

legend('Right Wing','Left Wing','Beak','Left Tail','Right Tail')
xlabel('X')
ylabel('Y')
zlabel('Z')
rotate3d on;

%% Animate Bird
row = 1;
limit = length(allPoints);

while row <= limit
    if isnan(allPoints(row,1)) ||isnan(allPoints(row,2)) ||isnan(allPoints(row,3)) ||isnan(allPoints(row,4)) ||isnan(allPoints(row,5)) ||isnan(allPoints(row,6)) ||isnan(allPoints(row,7)) ||isnan(allPoints(row,8)) ||isnan(allPoints(row,9)) ||isnan(allPoints(row,10)) ||isnan(allPoints(row,11)) ||isnan(allPoints(row,12))
        row = row + 1;
    else
        % Get beak reference point
        refBeak = [allPoints(row,7),... %x
                   allPoints(row,8),... %y
                   allPoints(row,9)];   %z
        %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
        % Get corresponding right wing reference point
        refRightWing = [allPoints(row,1),...    %x 
                        allPoints(row,2), ...   %y
                        allPoints(row,3)];      %z
        % Get vertical concatenation of beak and right wing
        beakRightWing = [refBeak; refRightWing];
        % Plot beak and right wing
        brw = plot3(beakRightWing(:,1), beakRightWing(:,2), beakRightWing(:,3),'-ok');
        %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
        % Get corresponding left wing reference point
        refLeftWing = [allPoints(row,4),...  %x 
                       allPoints(row,5), ... %y (There will be an error; it will still plot)
                       allPoints(row,6)];    %z Exception handling can be added later
        % Get vertical concatenation of beak and right wing
        beakLeftWing = [refBeak; refLeftWing];
        % Plot beak and right wing
        blw = plot3(beakLeftWing(:,1), beakLeftWing(:,2), beakLeftWing(:,3),'-ok');
        %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
        % Get corresponding right tail reference point
        refRightTail = [allPoints(row,13),...    %x
                        allPoints(row,14), ...   %y
                        allPoints(row,15)];      %z
        % Get vertical concatenation of beak and right wing
        beakRightTail = [refBeak; refRightTail];
        % Plot beak and right wing
        brt = plot3(beakRightTail(:,1), beakRightTail(:,2), beakRightTail(:,3),'-ok');
        %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
        % Get corresponding left tail reference point
        refLeftTail =  [allPoints(row,10),...    %x
                        allPoints(row,11), ...   %y
                        allPoints(row,12)];      %z
        % Get vertical concatenation of beak and right wing
        beakLeftTail = [refBeak; refLeftTail];
        % Plot beak and right wing
        blt = plot3(beakLeftTail(:,1), beakLeftTail(:,2), beakLeftTail(:,3),'-ok');
        
        %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
        % Save frame
        animBird = getframe(animPlot);
        im = frame2im(animBird);
        [imind,cm] = rgb2ind(im,256);
        % Write to the GIF File
        if row == 1
            imwrite(imind,cm,filename,'gif', 'Loopcount',inf);
        else
            imwrite(imind,cm,filename,'gif','WriteMode','append');
        end
        
        % Delete lines
        delete(blt), delete(brt), delete(blw), delete(brw);
        
        row = row + 1;
    end
end

[Walter Roberson]

Have you experimenting with deleting the existing file?

[Christopher Cochran]

I have-- I should state it works just fine on my laptop, but my desktop tends to have this error frequently.

Actually I just tried it again on my laptop and it didn't work. Whoops.

[Jose Espinosa]

What is your data matrix? I´m triying to figure it out

[Image Analyst]

Can you attach the m-files 'PlotRun3.m' and 'animateBird.m' and any data files that they need to read in?

[Walter Roberson]

Is it possible that on the laptop you are writing to a network drive?

[Christopher Cochran]

I uploaded the files.

Answer 1

[Christopher Cochran]

For anyone who was wondering: the row was beyond 1 in the if statement for appending the gif. I added a new counter so that there was an initial frame to append the gif to. In other words, the bottom part of the code is now:

        % Save frame
        animBird = getframe(animPlot);
        im = frame2im(animBird);
        [imind,cm] = rgb2ind(im,256);
        count = 1;
        % Write to the GIF File
        if count == 1
            imwrite(imind,cm,filename, 'gif', 'Loopcount',inf);
        else
            imwrite(imind,cm,filename, 'gif', 'WriteMode','append');
        end
        % Delete lines
        delete(blt), delete(brt), delete(blw), delete(brw);
        
        row = row + 1;
        count = count + 1;

[Kyriaki Kostoglou]

Thanks, was also trying to figure out why!

[RLeighton]

Same here - Thanks

[Walter Roberson]

That code always overwrites the GIF, since count = 1 followed by if count == 1 is always going to be true.

However, the original code had the problem that the isnan() could be true when row == 1, so testing row == 1 was not enough to know whether you had written anything to the gif. A counter initialized early on would be the fix for that.

[KCE]

I seem to be having this same issue and my count is initialized early on in my code.

clear all;
close all;
grid_box = [-5 50 -50 50]; %xmin xmax ymin ymax in km


for ik=1:361
    r11(ik)=30.*cos(ik*pi/180.);
    r12(ik)=30.*sin(ik*pi/180.);
end

for num=[20130519]
    YYYYMMDD=num2str(num);
    KXXX='KTLX';
    count=0;

    % Change directory to correct output file
    cd = 'cd ';
    %output = '/Users/djs78/Santellanes/RADAR/';
    output = strcat('/stens1/s0/kce115/radar/data/',YYYYMMDD,'/',KXXX,'/');
    fold = horzcat(output);
    %fold = horzcat(output,'NoCirc');
    chdir = horzcat(cd,output);
    status = system(chdir);
    fold

    % Add current folder to MATLAB path
    addpath(fold);

    % List the cfrad.*.nc files in the specified folder
    files = horzcat(fold,'/*.nc');
    disp(files);
    cfradfiles = dir(fullfile(files));
    [nofiles na] = size(cfradfiles);

    filecount = 0;

    for i = 1:nofiles
    % Identify each radar file individually
        filen = cfradfiles(i).name;

    % Read radar site from file
        radname = filen(50:53);

        file=filen;
        
        if str2num(filen(16:19))>1500
            count=count+1
%starts to grab info from the file
            radname = file(50:53);
            iSweepStart=ncread(file,'sweep_start_ray_index');
            iSweepEnd=ncread(file,'sweep_end_ray_index');
            elevs=ncread(file,'elevation');           %Netcdf radar data file
            timesec = ncread(file,'time');  %time in seconds since beginning of volume scan

% %%%%%%%%%%%%%%%%%%
% %Prompts you to pick elevation angle sweep
% %%%%%%%%%%%%%%%%%
            elevation_list = elevs(iSweepEnd);

            ZH=ncread(file,'REF');         %
            ZDR=ncread(file,'ZDR');        %Reads in the moment data from netcdf file

            sys_fdp = ncread(file,'r_calib_system_phidp');   %system diff phasew
            ray_n_gates=ncread(file,'ray_n_gates');    %Reads in some other
            azis=ncread(file,'azimuth');               %important attributes of the
            ranges_meters=ncread(file,'range');        %
            range_first_gate_meters = ranges_meters(1);   %Figures out range at first gate
            gate_spacing = ranges_meters(50)-ranges_meters(49);  %Should be 250 m for WSR-88Ds
            tempn = ncread(file,'nyquist_velocity');   %nyquist velocity at every azimuth.

            n_sweeps = numel(iSweepEnd);                %
            n_gates = ray_n_gates(iSweepStart+1);       %Figure out the number of 
            n_azis = (iSweepEnd-iSweepStart)+1;         %elements you have

    %Choose elevation angle. 2 is 0.5 degree, 4 is 0.9 degree.
    %djs test
            nrays=size(elevation_list,1);
            for nt=1:nrays;
                testelev=abs(elevation_list(nt)-1.5);
                if (testelev < 0.3)
                    pick_el=nt;
                end
            end
            %disp(pick_el);
            zz=pick_el;                                 %Stupid line.

            nyquist_vel = tempn(iSweepStart(zz)+1);
            azimuths = zeros(n_azis(zz),1);             %
            zh=zeros(n_azis(zz),n_gates(zz))-200.0;      %allocate some arrays
            vel = zh;
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%This part parses the CF-radial file into useable moment formats for the
%radar data moments: DATA(# azimuths, #range bins). Note that this is
%elevation sweep specific.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
            for xx=1:n_azis(zz)
                %Parse out indices based on sweep number zz   
                start_ind = sum(ray_n_gates(1:iSweepStart(zz)+xx)) - n_gates(zz) + 1;
                end_ind = sum(ray_n_gates(1:iSweepStart(zz)+xx));

                %Read in Reflectivity factor at horizontal polarization ZH
                zh(xx,1:n_gates(zz))=ZH(start_ind:end_ind);
                temp=find(zh(xx,:) == -200);
                zh(xx,temp) = NaN;
            end

            %populate the array of azimuths specific to the sweep
            azimuths(:) = azis(iSweepStart(zz)+1:iSweepEnd(zz)+1);

%---Thanks to Scott Ellis (NCAR), from whom I stole the next few bits-------
%find the size of arrays
            [m n]=size(zh);

%Get the arrays for polar coordinates
            r2 = range_first_gate_meters:gate_spacing:range_first_gate_meters+gate_spacing*(n-1);
            r2=r2./1000.0;
            theta = -(azimuths-90.0).*pi./180;

%Take the polar coordinates and transform to a regular cartesian grid. 
            [r,theta]=meshgrid(r2,theta);
            x1 = r .* cos(theta);
            y1 = r .* sin(theta);

%-------end Scott Ellis stolen code----------------------------------

            dualpol_colmap;  %calls colormaps for dualpol variables.
            scrsz = get(0,'ScreenSize');
            scandatetime=ncread(file,'time_coverage_start')';
            scandatetime=[scandatetime(1:10),' ',scandatetime(12:16),'Z'];
            radarname = ncreadatt(file,'/','instrument_name');
            degsym = ('^o');
            titl=([num2str(elevation_list(zz),3),degsym,' ',radarname,' ',scandatetime]);

            figure(1)

            set(gcf, 'Position', [1,1,1000,900]);
            pbaspect([2 2 2]);
            varplotted = ('Z_H');
            contourf(x1,y1,zh); axis(grid_box); shading interp; grid on; box on

            np = 64;
            z = zeros(np,np);
            x = linspace(0.0,1.0,np);
            x2d = repmat(x,np,1);
            z = x2d;
            colormap(zhmap)
            colorbar
            caxis([-20 75])
            hTitle  = title([varplotted, ' ', titl]);
            hXLabel = xlabel('x (km)','fontsize', 20);
            hYLabel = ylabel('y (km)','fontsize', 20);
            set(gca,'XTick',[-75,-50,-25,0,25,50,75]);
            set(gca,'XTickLabel',[-75,-50,-25,0,25,50,75]);
            set(gca,'YTick',[-75,-50,-25,0,25,50,75]);
            set(gca,'YTickLabel',[-75,-50,-25,0,25,50,75]);
            set( gca, 'FontName','Helvetica','FontSize',20,'FontWeight','demi');
            set([hTitle, hXLabel, hYLabel],'FontName','Helvetica');
            set([hXLabel, hYLabel],'FontSize',20,'FontWeight','demi');
            set(hTitle,'FontSize',20,'FontWeight','bold');
            set(gca,'Color','k')
            fig=1;

            set(gcf,'color','w'); % set figure background to white
            drawnow;
            frame = getframe(fig);
            im = frame2im(frame);
            [imind,cm] = rgb2ind(im,256);
            outfile = fullfile([file(7:14),varplotted,num2str(elevation_list(zz),3),'.gif']);
            if count==1
                imwrite(imind,cm,outfile,'gif','DelayTime',0.15,'loopcount',inf);
            else
                imwrite(imind,cm,outfile,'gif','DelayTime',0.15,'writemode','append');
            end
        end
    end
end