Undefined function 'rows' for input arguments of type 'double'.

How can I use the function "rows"? I have already installed the Database Toolbox but it is not working - or is it maybe the wrong toolbox? Thanks!

[Geoff Hayes]

Tim - how are you using the function rows? From the link, the only input to this function is a database cursor. Please post your code where you invoke rows and include any relevant code that precedes it.

If you are unsure if you have this function, type the following in the Commadn Window

 which rows -all

As I don't have the Database Toolbox, I observe the following

 'rows' not found.

What do you see when you run this command?

[Tim]

sam(:,4)  = [1:1:rows(sam)]'

where sam is a matrix with 3 columns and around 2000 rows. I'm not sure if that are enough information for you - that are all information I can give you so far. I'm using MATLAB for the first time so sorry for the unclear information.

When I type in

which rows -all

I get the file

Applications/MATLAB_R2014a.app/toolbox/database/database/@cursor/rows.m % cursor method

What does cursor method mean in this context? I cannot find good information here on the MATLAB site.

Thanks a lot and sorry for my little knowledge.

Answer 1

[Geoff Hayes]

Tim - the rows function of the Database Toolbox is to be used with a database cursor only where it is specified as an open SQL database cursor object generated using fetch. See fetch for details. So suppose you want to select some data/records from one or more tables in a database (Oracle, SQL Server, Sybase, etc). You write the SQL command to do this (something like select * from ... where ...) and then you execute this command against the database of interest. The cursor can then contain the records that are returned (which may include numeric, string, date, etc. data).

Since you are passing a 2000x3 matrix of data type double into the rows function, then the error makes sense - your matrix sam is not a cursor and so the Undefined function 'rows' for input arguments of type 'double' error message is raised.

What is your intent behind the line of code

 sam(:,4)  = [1:1:rows(sam)]'

You are setting the fourth column of sam to a column starting at one and incrementing by one until "something" is reached. What is that "something"?

If you are trying to determine the number of rows in sam, then use the size function as

 numRows = size(sam,1);

We use 1 since that corresponds to the first dimension of sam, which is the number of rows.