MATLAB: “for” loop question

baseline driftfor loop

Hello,

Below is an excerpt from my code, in which I wish to linearly fix a baseline drift. The variable "QLBrainShift1" is simply the original signal.

AmtOfPts1 = iSO(3) - iSO(2);  % Amount of points between SO 2 and 3
error1 = -QLBrainShift1(end);  % scalar
for point1 = AmtOfPts1:-1:0
    QLBrainShift1a = QLBrainShift1+error1-(point1/AmtOfPts1)*error1;
end
figure
plot(QTime(iSO(2):iSO(3)),QLBrainShift1a)

The plot that is being returned seems like QLBrainShift1a is being overwritten upon each loop. Therefore, only the last loop (point1=0) exits the "for" loop, and gets plotted. My intention is to create a new signal (QLBrainShift1a) according to the equation above with varying "point1" values, and plot all of the new signal on 1 graph. Any help is greatly appreciated.

Thanks, NH

Best Answer

Perhaps as follows? Basically, you've forgotten to index the element of QLBrainShift1a (and maybe also QLBrainShift1) that you're trying to operate on.

   point1=AmtOfPts1:-1:0;
   for i=1:length(point1)
    QLBrainShift1a(i) = QLBrainShift1(i)+error1-(point1(i)/AmtOfPts1)*error1;
   end

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MATLAB: Extracting data from an array

As Azzi mentions, it is not perfectly clear what you want as your output, but here is my best guess at the code you need:

A = [1 0 0.1
     2 0 0.3
     3 1 0.7
     4 2 0.4
     5 2 0.7
     6 1 0.8
     7 0 0.3
     8 0 0.7
     9 0 0.4
    10 1 0.7
    11 2 0.5
    12 2 0.1
    13 1 0.8
    14 0 0.2];
zeroIndices = find(A(:,2)==0);
numberZeros = numel(zeroIndices);
cellNumber = 0;
for nz = 1:numberZeros-1;
    if zeroIndices(nz+1) > zeroIndices(nz)+1
        cellNumber = cellNumber + 1;
        C{cellNumber} = A(zeroIndices(nz):zeroIndices(nz+1),:);
    end
end

Since you said you want "0 to 0", I included those rows. If you really only wanted the non-zero rows, use this instead:

C{cellNumber} = A(zeroIndices(nz)+1:zeroIndices(nz+1)-1,:);

MATLAB: Change plot color for increasing or decreasing x values

from what you described you don't really need a for loop to implement it. here is a solution to get away from a for loop

 %my attempt to make something i think you're plotting.  
 %something like a Hysteresis curve.  
  y = [0 8 12 8 0 -8 -12 -8  0];
  x = [2 10 10 8 -2 -10 -10 -8 2];
  figure,plot(x,y)
 %find which segments are heating and cooling or staying the same.  
  dx = diff(x); %takes x(n+1)-x(n) 
  heating = dx>0; %positive dx
  steady = dx ==0; %0 dx (temp values didn't change) 
  cooling = dx<0;  %negative dx.
plotSegmentX = [x(1:end-1);x(2:end)];  %pair the segments up.  

plotSegmentY = [y(1:end-1);y(2:end)];  %pair the segments up.  
%plot only the heating segments and color them red. then plot only the cooling etc.
figure,plot(plotSegmentX(:,heating),plotSegmentY(:,heating),'r',...
    plotSegmentX(:,cooling),plotSegmentY(:,cooling),'b',...
    plotSegmentX(:,steady),plotSegmentY(:,steady),'g')
xlim([-14 14]);ylim([-12 12])

Best Answer

Related Solutions

MATLAB: Extracting data from an array

MATLAB: Change plot color for increasing or decreasing x values

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