How to store the output of multiple for loops in an empty matrix in a particular order?

Question

Andi 2022-10-26

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1835438-how-to-store-the-output-of-multiple-for-loops-in-an-empty-matrix-in-a-particular-order

编辑： Andi 2022-10-26

Hi everyone,

My script consists of 2 loops with multiple conditions. For each iteration, I get an output that consists of 3 rows and 4 columns. I want to save this output in an empty matrix in sequential order. May someone suggest how I can do this?

Here is my attempt

T=[]
for kk=1:2
    s2=t_d(t_d(:,1)>= CE_L(kk) & t_d(:,1)<= CE_M(kk),:);
    s1=v_d(v_d(:,1)>= CE_L(kk) & v_d(:,1)<= CE_M(kk),:);
    for i=0:1:3;
            t1_f= addtodate(CE_L(kk), i, 'day');
            % multiple missing step to make the probelm simple 
            ww=1:length(tzcd);
            ph=abs(phz);
            phase=mean(ph);
            med=median(ph);
            st=std(ph);
            obb=i;
            res=[i phase med st];
            TT=[TT,res];
    end
    
end 

However this save outpout as an array, whereas i need as a matrix. My output is looks like this

0	 166.1	 167.0	 2.3	
0	 169.5	 166.4	 11.0	
0	 160.8	 162.9	 5.7	
0	 157.6	 151.7	 21.1

for each iteration of kk loop, where as each row represent the output of i iteration.

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Answer 1

Alex Hanes 2022-10-26

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https://ww2.mathworks.cn/matlabcentral/answers/1835438-how-to-store-the-output-of-multiple-for-loops-in-an-empty-matrix-in-a-particular-order#answer_1083623

编辑：Alex Hanes 2022-10-26

在 MATLAB Online 中打开

After each iteration of your for loop over i (for i=0:1:3 ... ), you replace the array, TT, that stores everything sequentially. Consider pre-allocating an array for TT and update after each loop, as you are already doing:

nk = 2; % number of iterations in your kk-loop
ni = 4; % number of iterations in your i-loop
nc = 4; % number of columns from your 'res' each loop
TT = zeros(nk*ni,nc); % pre-allocate

Now, instead of having TT = [TT,res]; in your code, replace it with:

for kk = 1:nk 
    for ii = 0:1:ni-1
        % Stuff
        
        idx = (kk-1)*ni + ii + 1; % calculate index
        TT(idx,:) = res; 
    end
end

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Andi 2022-10-26

在 MATLAB Online 中打开

@Alex Hanes thanks for help, but still there is this error

Unrecognized function or variable 'linInd'.
Error in untitled7 (line 113)
                    TT(linInd,:) = res;
                    
                    

Here is how i modified the script

clear all
clc
% BELOW SCRIPT IS FOR MULTIPLE DAYS CALCULATION
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
cd_ev=readmatrix('T_time.csv'); % 
ev_time=datenum(cd_ev(:,1),cd_ev(:,2),cd_ev(:,3),cd_ev(:,4),cd_ev(:,5),cd_ev(:,6));
CE_M=ev_time';
for jj=1:29
     b=CE_M(:,jj);
     aa(jj)= addtodate(b, 5, 'day');
     bb(jj)= addtodate(b, -5, 'day');
end 
CE_U=aa;
CE_L=bb;
% % ------------ Data Set 2:  -------------%
s_tid=dlmread('TID.csv', ',', 1, 1);
t1=datenum(s_tid(:,1),s_tid(:,2),s_tid(:,3),s_tid(:,4),s_tid(:,5),s_tid(:,6)); 
t_d=[t1 s_tid(:,7)];
%------------- Data Set 3:  --------------% 
s_ven=dlmread('VENT.csv', ',', 1, 1);
ts=datenum(s_ven(:,1),s_ven(:,2),s_ven(:,3),s_ven(:,4),s_ven(:,5),s_ven(:,6)); 
v_d=[ts s_ven(:,7)];
% ---------- Data selection for a particular event ---------%
%tt=[];
nk = 2; % number of iterations in your kk-loop
ni = 4; % number of iterations in your i-loop
nc = 4; % number of columns from your 'res' each loop
TT = zeros(nk*ni,nc); % pre-allocate
for kk=1:2
    s2=t_d(t_d(:,1)>= CE_L(kk) & t_d(:,1)<= CE_M(kk),:);
    s1=v_d(v_d(:,1)>= CE_L(kk) & v_d(:,1)<= CE_M(kk),:);
    ser1=s1(:, 2)-mean(s1(:,2)); % series 1 minus its mean
    ser2=s2(:, 2)-mean(s2(:,2)); % series 2 minus its mean
    ta=s1(:, 1);
    ta1=(ta-ta(1));
    tb=s2(:, 1);
    tb1=(tb-tb(1));
%     figure(1); 
%     subplot(211); 
%     plot(ta1,ser1,'-b'); 
%     legend('Vent Fluid')
%     title('Vent Fluid Temp'); grid on
%     subplot(212); 
%     plot(tb1,ser2,'r-'); 
%     title('Tidal Height'); grid on
%     xlabel('Time (days)')
%     legend('Tidal')
%     obb=zeros(1,20);        %allocate array for phase angles
%     phase=zeros(1,20);        %allocate array for estimates of dominant frequency
    for i=0:1:3;
             t1_f= addtodate(CE_L(kk), i, 'day');
             t2_f= addtodate(CE_L(kk), i+2, 'day');
             sf2=t_d(t_d(:,1)>= t1_f & t_d(:,1)<= t2_f,:);
             sf1=v_d(v_d(:,1)>= t1_f & v_d(:,1)<= t2_f,:);
             if length(sf1) ~= length(sf2)
                continue;
            end
            S=[sf1 sf2];
            tfa=sf1(:, 1);
            tfa=(tfa-tfa(1));  %time (days) (initial offset removed)
            sff1=S(:, 2)-mean(S(:,2)); % series 1 minus its mean
            sff2=S(:, 4)-mean(S(:,4)); % series 2 minus its mean
            N=length(tfa);
            dt=(tfa(end)-tfa(1))/(N-1); %sampling interval (days)
            fs=1/dt;  fNyq=fs/2;    %sampling frequency, Nyquist frequency (cycles/day)
            f1=1; f2=4;             %bandpass corner frequencies (cycles/day)
            [z,p,k]=butter(4,[f1,f2]/fNyq,'bandpass');  %4th order Butterworth bandpass filter coefficients
            [sos,g]=zp2sos(z,p,k); %sos representation of the filter
            y1=filtfilt(sos,g,sff1);  %apply zero phase filter to ser1
            y2=filtfilt(sos,g,sff2);  %apply zero phase filter to ser2
            %     % %--------- Zero crossing time --------%
% 
            zci = @(v) find(diff(sign(v))>0);  %define function: returns indices of +ZCs
            izc1=zci(y1);                      %find indices of + zero crossings of y1
            izc2=zci(y2);                      %find indices of + zero crossings of y2
            ZeroX = @(x0,y0,x1,y1) x0 - (y0.*(x0 - x1))./(y0 - y1); % Interpolated x value for Zero-Crossing 
            ZT1 = ZeroX(tfa(izc1),y1(izc1),tfa(izc1+1),y1(izc1+1));
            ZT2 = ZeroX(tfa(izc2),y2(izc2),tfa(izc2+1),y2(izc2+1));
                if length(ZT1)==length(ZT2)
            tzcd=ZT1-ZT2;          %zero crossing time differences
                elseif length(ZT1)==length(ZT2)-1
            tzcd=ZT1-ZT2(1:end-1); %zero crossing time differences
                elseif length(ZT1)-1==length(ZT2)
            tzcd=ZT1(2:end)-ZT2;   %zero crossing time differences
                end
            fdom=(length(ZT2)-1)/(ZT2(end)-ZT2(1));
            phz=360*fdom*tzcd;          %phase lag of y1 relative to y2 (degrees)
            ww=1:length(tzcd);
            ph=abs(phz);
            phase=mean(ph);
            med=median(ph);
            st=std(ph);
            obb=i;
            res=[i phase med st];
            for kk = 1:nk 
                for ii = 0:1:ni-1
                    idx = (kk-1)*ni + ii + 1; % calculate index
                    TT(linInd,:) = res; 
                end
            end
    end
    
end 