You aren't going to get very good smoothing with such a small amount of data, but here is one possibility (of many):
data = [ ...
1 NaN
2 1.356390367
3 1.295994741
4 1.50041999
5 2.790612162
6 4.62246207
7 6.134079946
8 6.818989019
9 7.953940954
10 7.2993
11 10.4519388
12 12.4768
13 10.6323
14 NaN
15 11.94706861
16 6.180212227
17 7.622561145
18 6.229011638
19 4.09315833
20 2.495924367
21 2.213217555
22 2.735480781
23 2.071762287
24 1.69211523
];
plot(data(:,1), data(:,2))
hold on
sm_data = smoothdata(data(:,2), 'sgolay'); % save the smoothed data
plot(data(:,1), sm_data)
grid on
legend('original data', 'smoothed data')
