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# how to draw vertical lines on the plot?

Asked by Olga on 14 Mar 2012

Hello, I'm doing HRV spectral analysis and I want draw vertical lines around freq bands on my plot. It'd be great if each area could be in different colour. If anyone could give me any tip, shall be very grateful ;)

I need to add this to this plot:

```%Calculate PSD
[PSD,F] = pwelch(odstepRR,128,64,[],fs); %uses a hamming window
```
```      VLF = [0.0033 0.04];
LF = [0.04 0.15];
HF = [0.15 0.4];```
```      % find the indexes corresponding to the VLF, LF, and HF bands
iVLF= (F>=VLF(1)) & (F<=VLF(2));
iLF = (F>=LF(1)) & (F<=LF(2));
iHF = (F>=HF(1)) & (F<=HF(2));```
```      % calculate areas, within the freq bands (ms^2)
aVLF=trapz(F(iVLF),PSD(iVLF));
set(handles.vlf, 'string', num2str(aVLF));
aLF=trapz(F(iLF),PSD(iLF));
set(handles.lf, 'string', num2str(LF));
aHF=trapz(F(iHF),PSD(iHF));
set(handles.hf, 'string', num2str(aHF));
aTotal=aVLF+aLF+aHF;
set(handles.tp, 'string', num2str(aTotal));```
```      %calculate LF/HF ratio
lfhf =aLF/aHF;```
```axes(handles.axes5);
set(handles.text45, 'visible', 'on')
set(handles.axes5, 'visible', 'on')
```
```%plot area under PSD curve
area(F(:),PSD(:),'FaceColor',[.6 .6 .6]);
```
```grid on;
```

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Answer by Walter Roberson on 14 Mar 2012
```line([X X], [LowY HighY])
```

for example,

```line([5 5], [0.1 17])
```

to draw a line from (5,0.1) to (5,17)