How to Find Number of Rows

[ppal]

Prime 8 . No file attached. Trivial inputs. How do I get 3 ?

[terryhendicott · Accepted solution]

Hi

Default start of counting of rows is 0 if not defined as anything else by ORIGIN value.

Defined rows 3 to 5.  0 to 2 rows will have zero. Check by M[0=.

so 6 rows in M.

Cheers

Terry

[ppal]

[Werner_E]

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How do I get 3 ?

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Thats easy - you get 3 if you use a vector or matrix with just three rows. 😉

But the vector M you created has six elements for reason which Terry already explained.
So its correct to say that has six rows.

Give it a try yourself and type M=  You will see a six rows vector.

BTW, when you try rows(i) or rows(M[i) you feed the elements 3,4,5 one after the other in the rows() function. Each of these values is a scalar, not a matrix or vector and so the row() function returns 0 for every of these three values and thats the reason for the vector with three zeros you get as a result.

If you want to create a three element vector with the values 3,4,5, here is the way to go

You could also do it that way

but I would recommend the first approach.

You may even do it that way

but I would strongly advise against it.

[ppal]

Thanks. First approach will do. 

[LucMeekes]

"If you want to create a three element vector with the values 3,4,5"...

You forgot the simplest one:

and my favourite:

Luc

[Werner_E]

Yes, you are right. And they also have the benefit of being ORIGIN-independent.

Here are a few more ... 😉

If needed more often, a utility function could be handy

And here a version which should also work in Express