MATLAB: Plotting two vectors/arrays/curves with different distribution intervals as a single curve

Question

Suppose that I'd like to plot y1+y2 against x for the interval of [120,480]

x  y1  x  y2
24  1.4050  15  9.4526
48  0.8348  30  7.7970
72  1.0272  45  6.8056
96  1.2513  60  6.0248
120  1.5518  75  5.3847
144  2.1398  90  5.1452
168  3.2061  105  4.7522
192  3.6026  120  4.4740
216  3.0298  135  4.2774
240  1.9868  150  4.1293
264  1.4370  165  4.1693
288  1.1396  180  4.0630
312  0.9630  195  4.1130
336  0.9592  210  4.1511
360  0.8783  225  3.8805
384  0.8384  240  3.7559
408  0.8365  255  3.3221
432  0.8786  270  2.9122
456  1.0791  285  2.5477
480  1.2648  300  2.2394
504  1.3586  315  2.1261
528  1.0697  330  1.9013
552  0.7656  345  1.7193
576  0.5927  360  1.5759
600  0.5203  375  4.4740
624  0.5067  390  4.2774
648  0.5604  405  4.1293
672  0.6357  420  4.1693
696  0.7245  435  4.0630
720  0.7881  450  4.1130
744  0.7481  465  5.1722
768  0.6318  480  3.8805
792  0.4802  495  3.7559
816  0.3621  510  3.3221
840  0.2903  525  2.9122
864  0.2413  540  3.8805
888  0.2350  555  3.7559
912  0.2552  570  3.3221
936  0.2558  585  4.1293
960  0.2213  600  3.3333

This data is an example so do not create a logic for the data. Only a generic code will be helpful. Thanks.

Answer 1

Data = [24  1.4050  15  9.4526
 48  0.8348  30  7.7970
 72  1.0272  45  6.8056
 96  1.2513  60  6.0248
 120  1.5518  75  5.3847
 144  2.1398  90  5.1452
 168  3.2061  105  4.7522
 192  3.6026  120  4.4740
 216  3.0298  135  4.2774
 240  1.9868  150  4.1293
 264  1.4370  165  4.1693
 288  1.1396  180  4.0630
 312  0.9630  195  4.1130
 336  0.9592  210  4.1511
 360  0.8783  225  3.8805
 384  0.8384  240  3.7559
 408  0.8365  255  3.3221
 432  0.8786  270  2.9122
 456  1.0791  285  2.5477
 480  1.2648  300  2.2394
 504  1.3586  315  2.1261
 528  1.0697  330  1.9013
 552  0.7656  345  1.7193
 576  0.5927  360  1.5759
 600  0.5203  375  4.4740
 624  0.5067  390  4.2774
 648  0.5604  405  4.1293
 672  0.6357  420  4.1693
 696  0.7245  435  4.0630
 720  0.7881  450  4.1130
 744  0.7481  465  5.1722
 768  0.6318  480  3.8805
 792  0.4802  495  3.7559
 816  0.3621  510  3.3221
 840  0.2903  525  2.9122
 864  0.2413  540  3.8805
 888  0.2350  555  3.7559
 912  0.2552  570  3.3221
 936  0.2558  585  4.1293
 960  0.2213  600  3.3333];
x1 = Data(:, 1);
y1 = Data(:, 2);
x2 = Data(:, 3);
y2 = Data(:, 4);
x   = linspace(240, 480, 100);  % or linspace(240, 480, 400) or whatever you want
y12 = interp1(x1, y1, x) + interp1(x2, y2, x);
plot(x, y12)
hold
plot(x1,y1, 'r')
plot(x2,y2, 'g')