Adding a linear line of best fit to subplots

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Jonathan O'Neill
Jonathan O'Neill on 30 Jan 2015
Commented: Jonathan O'Neill on 30 Jan 2015
I have been looking up matlab help on this but I cant seem to get my head around it. For example when I look at my code I just have:
plot (SigVal)
So when I try and plot:
polyval(x, y 1)
I have nothing to put between these brackets except "SigVal". Can someone talk me through how I go about adding a line of best fit to this subplot?
thanks
%-------------------------------------- SIG VAL SUBPLOT -------------------
figure('name','resultimage');
Len=1400;
Wid=600;
aa=25;
bb=200;
set(gcf,'position',[aa bb Len Wid]);
subplot(2,3,1)
xmin=1;
xmax=100;
plot(SigVal)
h=plot(SigVal);
% label max and min values of a 'fn1' on the plot
xValue = get(h,'XData');
yValue = get(h,'YData');
imin = find(min(yValue)==yValue);% find the index for the min and max
imax = find(max(yValue)==yValue);% values of yValue
(yValue(imax));
(yValue(imin));
% label the max. and min. values on the plot
ymax=yValue(imax)+3;
ymin=yValue(imin)-3;
y1=ymax-1;
y2=y1;
y3=ymin+1;
maxstr=['max.=',num2str(yValue(imax))];
minstr=['min.=',num2str(yValue(imin))];
text(10, y1, maxstr);
text(50, y2, minstr);
if Signalstabilitytestfail == 1;
Test_resultstr = 'Test FAILED';
text(30, y3, Test_resultstr)
sigvalteststr='fail';
else
Test_resultstr = 'Test passed';
text(30, y3, Test_resultstr)
sigvalteststr='pass';
%warndlg('Signal Stability failed','!! Warning !!')
end
axis([xmin xmax ymin ymax])
title('SigVal')

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Accepted Answer

Image Analyst
Image Analyst on 30 Jan 2015
See my attached polyfit demo. I think it should answer your questions.
  1 Comment
Jonathan O'Neill
Jonathan O'Neill on 30 Jan 2015
Thank you, I found some code you provided to answer another question and followed that...
http://www.mathworks.com/matlabcentral/answers/89335-how-do-i-make-a-best-fit-line-along-with-getting-r-2-on-matlab
I replaced my code and it worked, although it gave me a graph with dots, in order to have the dots connected I did this...
Changing
"h=plot(x, y, 'b*', 'LineWidth', 1, 'MarkerSize', 1";
to
"h=SigVal" gave me connected lines and that seems to be all it affected.
%-------------------------------------- SIG VAL SUBPLOT -------------------
figure('name','resultimage');
Len=1400;
Wid=600;
aa=25;
bb=200;
set(gcf,'position',[aa bb Len Wid]);
subplot(2,3,1)
xmin=1;
xmax=100;
x=1:100
y = SigVal
plot(x, y, 'b*', 'LineWidth', 1, 'MarkerSize', 1);
coeffs = polyfit(x, y, 1);
% Get fitted values
fittedX = linspace(min(x), max(x), 200);
fittedY = polyval(coeffs, fittedX);
% Plot the fitted line
hold on;
plot(fittedX, fittedY, 'r-', 'LineWidth', 1);
********************************************************
%h=plot(x, y, 'b*', 'LineWidth', 1, 'MarkerSize', 1);
h=plot(SigVal);
********************************************************
% label max and min values of a 'fn1' on the plot
xValue = get(h,'XData');
yValue = get(h,'YData');
imin = find(min(yValue)==yValue);% find the index for the min and max
imax = find(max(yValue)==yValue);% values of yValue
(yValue(imax));
(yValue(imin));
% label the max. and min. values on the plot
ymax=yValue(imax)+1.5;
ymin=yValue(imin)-1.5;
y1=ymax-1;
y2=y1;
y3=ymin+1;
maxstr=['max.=',num2str(yValue(imax))];
minstr=['min.=',num2str(yValue(imin))];
text(10, y1, maxstr);
text(50, y2, minstr);
if Signalstabilitytestfail == 1;
Test_resultstr = 'Test FAILED';
text(30, y3, Test_resultstr)
sigvalteststr='fail';
else
Test_resultstr = 'Test passed';
text(30, y3, Test_resultstr)
sigvalteststr='pass';
end
axis([xmin xmax ymin ymax])
title('SigVal')

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