time interval and associated elapsed time

I have dataset of 1000 entries with date and magnitude column.i want to calculate the elapsed time between first hundred entries entry in days.same for second hundred enries,third hundred entries and so on ...

Answer 1

[Walter Roberson]

groupsize = 100;
startdates = YourArray(1:groupsize:end,1);
enddates = YourArray(groupsize:groupsize:end,1);
elapsed = enddates - startdates;

The units will be the same as the units for your date information.

I suspect that what you want is instead

groupsize = 100;
startdates = YourArray(1:groupsize:end,1);
elapsed = diff(startdates);

That is, the first time would be the difference between the 101'st date and the 1'st date, then the 201's to the 101'st: the time difference between the blocks. What you asked is that the first one would be the 100'th to the 1'st, the 200th to the 101'st, so the difference within the block, not the difference between adjacent blocks.

[Seemab Janjua]

Thanks sir Walter Roberson.Sir this is my typing mistake and your suspect was right.