Resetting index of filtered data in Matlab

Hi,

I have time information of length N from matrix X in below format

% Matrix X

Time_ms Data

100 ....

200

300

400

....

N

I have another matrix whose length is more than this previous time array. Matrix is like below

% Matrix Y

Time(ms) satx_pos saty_pos satz _pos

100 25312593 8315787 -97412.2

110 -5471969 20037795 16498179

120 .... ..... .....

130 ... ..... ...

.... ...... ......... ......

200 ..... .... ......

210 ......... ............ .......

.....

300

....

My goal is to match those rows which has same time as previous time vector and reset the index.

I am able to compare and match the rows using for loop but not able to reset the index. How can I achieve it so that finally I can concatenate the 2 matrix and form a single matrix for easy array operation.

Thanks