I need to plot a line over my imagesc

I have checked matlabcentral but not found the write one i need to plot a line which starts from a point on the y-axis to the corner of the image that is to the end of x-axis

[raj]

I have a spectrogram of a chirp signal i need to plot a line over

the chirp signal hope it makes things clear

Answer 1

[Walter Roberson]

xoff = 7.38;       %for example. Start drawing from (xoff,0)
ymax = get(gca, 'YLim');
hold on
plot([xoff xoff], [0 ymax], 'r:');  %change r: as needed

Note: This will draw a line according to the current top of the x axis. The details of this method will have difficulty if you pan or zoom.

I was unsure about where you wanted the line to go. If you want it to go along the y-axis to the end of the x-axis, then

xoff = 7.38;       %for example. Start drawing from (xoff,0)
xmax = get(gca, 'XLim');
hold on
plot([xoff xmax], [0 0], 'r:');  %change r: as needed