If I understand correctly, move the section of data from x=1.25 to x=2.1 and place that segment just before x=0.
Assuming you have two variables x & y that were used to plot your data: plot(x,y),
segmentStart = 1.25;
segmentStop = 2.1;
placeBefore = 0;
newIdx = [...
find(x<min(placeBefore, segmentStart)), ... %index values prior to insertion point
find(x>=segmentStart & x<=segmentStop), ... %index values of segment to be moved
find(x>=0 & x<segmentStart), ... %index values of section between insertion point and start of segement
find(x>segmentStop),... %indes values following the segment
];
plot(x, y(newIdx))
