View Full Version : Array.....what is a row & what is a column?

 Fess10 October 2005, 02:38 AMHello, I'm currently reading "Complete Maya Programming" by David Gould. I'm confused about what is a row & what is a column, can some one advise me on this using the below example................ This is from P.74: Single Dimentional Array that holds two-demensional data: int \$pixs[] = { 1, 2, 3, 4, 5, 6, 7, 8} ; To find out what the single array index is that corresponds to a given row and column, the following formula is used: index = row x number_of_columns + column All indices are base 0. So to access row 1 (second row), column 3 (fourth column), you would do the following: int \$nCols = 4 int \$index = 1 * \$nCols + 3; print \$pixs[\$index]; // Result: 8 Thanks Fess
10 October 2005, 05:39 PM
row = [1,2,3,4]

[1
column = ,2
,3
,4]

i think he is talking about the fact that you can build a 2d array from values, e.g. a matrix and you can find the position in the array of the value. So to take his example and the one above you'd make it like this

[1,2,3,4] (The [ would stretch across both.)
5,6,7,8

Fess
10 October 2005, 08:42 PM

Thanks for responding.

This book was going well with "explaination" and all of a sudden I turned the page and he starts throwing all this complex code at me without details of "how & why"........sigh.

I simple don't understand the defination of "column"
using this as a example:

martix \$m[2][4] = << 3, 4, 6, 7; 3, 9, 0,1 >>; (okay, the matirx \$m has 2 rows, first row is 3,4,6,7 and second rown is 3, 9, 0, 1 right?) Where or what the heck are the colums?

print ( \$m [0][0] ); // Result: 3 (this is saying print print row 0 and column 0, how did it get "3"?)

print ( \$m [1][3] ); // Result: 1 (this is saying print print row1 and column 2, row 1 is 3, 4, 6 7 and column is ????)

Thank you
Fess

goleafsgo
10 October 2005, 09:00 PM
3 4 6 7
3 9 0 1

Above is your example...so (3,4,6,7) is the first row and (3,3) is the first column, (4,9) is the second column, (6,0) is the third column and (7,1) is the fourth column.

The element that is in the first row and first column would be 3...which is what you are asking for when you say \$m[0][0]. If you print \$m[1][2] you should get 0.

Does that help at all?

10 October 2005, 09:50 AM
columns are the numbers from top to bottom, like goleafsgo said

row
----->
1 2 3 4 |
5 6 7 8 | column
9 1 2 5 V

Just think of column like a column in real life, holding up part of a building, its just soming that goes up and down at a position.

at the moment, don't worry too much about matrices, yes they are important for transformations, converting points from one space to another etc, but you really won't use them too much (or at least I haven't yet).

Here is a useful page:

http://chortle.ccsu.edu/VectorLessons/vmch13/vmch13_1.html

Fess
10 October 2005, 03:27 AM
goleafsgo,

Your explaination did the trick. I understand the whole row/column layout now. Put that together with indices based 0, it all makes sense :thumbsup:

I'll check that link out, thanks. Cool way to think about "rows" & "columns"

Thank you
Fess

thematt
10 October 2005, 07:40 AM