Comments on: Inserting Rows

By: jiro

jiro — Tue, 01 Nov 2011 15:16:50 +0000

@saeedeh,

Did you download the function “insertrows” from the File Exchange? The link is in the beginning of this blog post.

By: saeedeh

saeedeh — Tue, 01 Nov 2011 09:34:36 +0000

Thank you very much for your information about inserting a row to matrix in matlab
I tried it but it seems it doesnot work in matlab 2009!
am I right?
will you please tell me how can I use this in my version?
thanks again

By: Abiyu

Abiyu — Wed, 22 Jul 2009 20:32:09 +0000

Thank you so much!
It really was tremendous help!

Abiyu

By: jiro

jiro — Thu, 29 May 2008 00:19:54 +0000

Nice job, Rob. Thanks for posting the file.

I like that you included error checking in the function to make it robust to user errors.

By: Rob S.

Rob S. — Wed, 21 May 2008 13:52:52 +0000

Jiro,

Your pick this week is similar to a small, modular function I use called “putBinA”. It plants a 2D matrix B into a larger 2D matrix A, with the upper-left corner of B at the given coordinates. It qualifies as a “simple function” you asked for, so I posted it to the file exchange (19989).

Coincidentally, putBinA was also bundled into a previous function that paginates multi-page tif files (scanned documents), which is also in the file exchange (17634).

Hope this is what you’re looking for.

By: Tim Davis

Tim Davis — Sun, 18 May 2008 10:13:41 +0000

Impressive performance on large sparse matrices. I tried it on a matrix of dimension 445,315 and 7,479,343 nonzeros (UFget(914) if you want to play with it; a large DNA model). It took about 8 seconds to insert 42 rows, as compared with about 1.5 seconds just to do C=A’.

That’s impressive because fiddling with the rows of a sparse matrix can easily take O(k*nnz(A)) time, if you do the wrong thing on k rows one at a time. This function gets it right.

Cool!

By: Brett

Brett — Fri, 16 May 2008 15:09:21 +0000

Very useful function, Jiro (and Jos!). I like that 0 works as an index; that makes it easy to interlace matrices A and B, starting _above_ the first row of A. So, for instance:
>> A = magic(3); B = rand(3); C = insertrows(A,B,0:2)
C =
0.0971 0.3171 0.4387
8.0000 1.0000 6.0000
0.8235 0.9502 0.3816
3.0000 5.0000 7.0000
0.6948 0.0344 0.7655
4.0000 9.0000 2.0000

Also, note that with a few transpose operators, INSERTROWS does double duty as INSERTCOLS:
>> D = insertrows(A’,B’,0:2)’
D =
0.0971 8.0000 0.3171 1.0000 0.4387 6.0000
0.8235 3.0000 0.9502 5.0000 0.3816 7.0000
0.6948 4.0000 0.0344 9.0000 0.7655 2.0000

I haven’t tried out Duane’s submission yet, but I’m going to keep Jos and Duane in mind when I need to flexibly intersperse matrices!