find result - Empty matrix: 0-by-1 - but it's wrong

Question

Céline Bachelier 2014-5-15

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https://ww2.mathworks.cn/matlabcentral/answers/129724-find-result-empty-matrix-0-by-1-but-it-s-wrong

回答： Céline Bachelier 2014-5-15

采纳的回答： Céline Bachelier

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hello,

I have a problem with the 'find' command. this is my code:

ligne_journaliere = find (data_output_1(:,3)==2 & data_output_1(:,4)==3);

j = data_output_1(ligne_journaliere(1),4);

while data_output_1(ligne_journaliere,3)==2

    figure('units','pixels','Position',[1 41 1600 784]);
    [AX,h1,h2] = plotyy(timestamp(ligne_journaliere),sal(ligne_journaliere),timestamp(ligne_journaliere),lat(ligne_journaliere)'.');
    set(h1,'linestyle','.','color','b','markersize',6);
    set(h2,'linestyle','.','color',[0 0.8 0],'markersize',6);
    datetick(AX(1));
    datetick(AX(2));
    hold on
    grid on;
    min_sal_jour = min(sal(ligne_journaliere));
    max_sal_jour = max(sal(ligne_journaliere));
    mois_du_jour = data_output_1(ligne_journaliere,3);
    jour_du_jour = data_output_1(ligne_journaliere,4);
    title(['Salinity - ',date_data,'/',num2str(mois_du_jour(1)),'/',num2str(jour_du_jour(1)),' - ', 'min sal = ',num2str(min_sal_jour),' - ','max sal = ',num2str(max_sal_jour)]);
    xlabel('Time');
    ylabel(AX(1),'Salinity');
    ylabel(AX(2),'Latitude');
    hgexport(gcf,[path_data_output,'MD_salinity_journaliere_',date_data,'_',num2str(mois_du_jour(1)),'_',num2str(jour_du_jour(1))],hgexport('factorystyle'),'Format', 'jpeg');
    j = data_output_1(ligne_journaliere(end)+1,4);
    ligne_journaliere = find (data_output_1(:,3)==2 & data_output_1(:,4)==j)

end

And 'ligne_journliere' just before the 'end' = Empty matrix: 0-by-1 when next j =j+2 and not j+1 ( j = days, but i don't have data everyday), and it's wrong find must return something.

I don't see the problem.

can you help me with that please. Céline