Matlab: Shifting a graph (setting a different start position) - matlab

Question

I am working with this code to import a spread sheet containing x (angle) and y (intensity) axes and plot the results:
%% Initialize variables
filename = ['C:\Users\themosawi\Desktop\khalifadec2104\mih10distracks-azi\mih10-distal-2_5mmbelowDH\mih10distracks_0363.dat'];
startRow = 5;
%% Format string for each line of text:
formatSpec = '%14f%f%[^\n\r]';
%% Open the text file.
fileID = fopen(filename,'r');
%% Read columns of data according to format string.
dataArray = textscan(fileID, formatSpec, 'Delimiter', '', 'WhiteSpace', '', 'HeaderLines' ,startRow-1, 'ReturnOnError', false);
%% Close the text file.
fclose(fileID);
%% Allocate imported array to column variable names
angle = dataArray{:, 1};
intensity = dataArray{:, 2};
%% Plot
plot(angle, intensity)
Sometimes I get plots looking like this (in which the plotting starts at the middle of the peak):
I would like the plotting to start from angle 45 instead of angle 0 (in the x-axis) so I can identify both peaks.
Here is the file:
http://mosawi.co.uk/mih10distracks_0363.dat

Answer 1

Try the code below, it may work:
%% Initialize variables
filename = ['C:\Users\themosawi\Desktop\khalifadec2104\mih10distracks-azi\mih10-distal-2_5mmbelowDH\mih10distracks_0363.dat.txt'];
startRow = 5;
%% Format string for each line of text:
formatSpec = '%14f%f%[^\n\r]';
%% Open the text file.
fileID = fopen(filename,'r');
%% Read columns of data according to format string.
dataArray = textscan(fileID, formatSpec, 'Delimiter', '', 'WhiteSpace', '', 'HeaderLines' ,startRow-1, 'ReturnOnError', false);
%% Close the text file.
fclose(fileID);
%% Allocate imported array to column variable names
angle = dataArray{:, 1};
intensity = dataArray{:, 2};
%% New angle & Intensity
lap = 100; % // Enter any angle value in range of your angle data
ind = find(angle > lap -.4 & angle < lap + .6);
newAngle = linspace(angle(ind), angle(ind)+angle(end), length(angle));
newIntensity = [intensity(ind:end); intensity(1:ind-1)];
%% Plot
plot(newAngle, newIntensity)
What I got as output:

Answer 2

Here's one approach, working with the cyclical nature of the data:
angle = angle(:).'; % ensures that these are both row
intensity = intensity(:).'; % vectors (may be unnecessary)
plot( [ angle-360 angle angle+360 ], [ intensity intensity intensity ] )
xlim( [0 360] + 45 ) % or +/- whatever you want

Answer 3

I'm not 100% sure I got your question right, but this is what I would do to phase shift this plot:
If so, you could replace:
%% Plot
plot(angle, intensity)
with
%% Plot
shift_angle = 45;
plot(angle, [intensity(shift_angle:end) ; intensity(1:shift_angle-1)])