Consider preallocating for speed

Matlab tells me in line 11 to consider preallocating, but when I try to do it with line 7, matlab is still not happy with it. The value "Werte" is (1,16) in line 8 and in line 11 I add +1. I searched the forums but couldn't find a solution. What can i do?

1 while true
2    tic
3    data=importdata('C:\Users\Hüs\Documents\MATLAB\Datalogger\KlimaLoggProAuto.dat1');
4    alle=[data(8,1);data(11,1);data(21,1);data(24,1);data(34,1);data(37,1);data(47,1);data(50,1);data(60,1);data(63,1);data(73,1);data(76,1);data(86,1);data(89,1);data(99,1);data(102,1)];
5    string(alle);
6    a=split(alle,'"');
7    Werte=zeros(1,17); %preallocated value....might be unused.
8    Werte=a(:,2)';
9    Zeit=datetime('now');
10   Zeit=string(Zeit);
11   Werte=[Zeit Werte]; %Consider preallocating for speed.
12   Werte=cellstr(Werte);
13   [succes,message]=xlsappend('Datalogger.xlsx',Werte,1);
14   pause(600-toc)
15 end

Answer 1

[Bjorn Gustavsson]

In your code you change the values and type of Werte 4 times. That seems a bit excessive. I'd try something like this:

1 while true
2    tic
3    data = importdata('C:\Users\Hüs\Documents\MATLAB\Datalogger\KlimaLoggProAuto.dat1');
4    alle = [data(8,1);data(11,1);data(21,1);data(24,1);data(34,1);data(37,1);data(47,1);data(50,1);data(60,1);data(63,1);data(73,1);data(76,1);data(86,1);data(89,1);data(99,1);data(102,1)];
5    string(alle);
6    a = split(alle,'"');
7    % Overwritten on the very next line: Werte=zeros(1,17); %preallocated value....might be unused.
8    Werte = a(:,2)';
9    Zeit = datetime('now');
10   Zeit = string(Zeit);
11   % Seems skippable: Werte=[Zeit Werte]; %Consider preallocating for speed.
12   ZeitWerte_string = cellstr([Zeit,Werte]);
13   [succes,message] = xlsappend('Datalogger.xlsx',ZeitWerte_string,1);
14   pause(600-toc)
15 end

HTH

[Hüseyin Uzun]

Thanks a lot. It works =)