Replace part of a column in a matrix with different values

Hi all,

I have a matrix C, its size is dependent on some non-dimensional variables I have previously defined. Initially, C has a constant value (=1) in column one, and zeros else. However, I need to redefine part of the first column in C. More specifically, I need to define the last 3/4 rows of C (represented by a dimensionless variable [LLY] ). However, when doing so I yield a non-integer value:

length_x= LLX/dx <== dx,LLX dimensionless
length_y= LLY/dy; <== dy,LLY dimensionless
C=zeros(length_y,length_x);
A=.25*LLY
C(A:LLY,1)=1;

~~~~

EDU>> LLY
LLY =
   1
~~~

Where LLY represents a dimensionless length. With units, LLY has the length of 2000, I would like to redefine the values in column one for rows 500 through 2000 with a value of 1. However, because of the nature of non-dimensional variables LLY is defined to be 1.

I cannot pre-define C with dimensions (units) because the resulting matrix will be too large for Matlab, thus why I need to make it dimensionless. Any ideas how to overcome the resulting non-integer value of 0.25?

~~~~~
EDU>> A
A =
  0.2500
~~~~~

Thank you in advance, Kevin

Answer 1

[Cedric]

This is a valid approach only when LLY is a multiple of 4. I am unsure what it is that you want to achieve, but if you want to guarantee that A is an integer such as 1 <= A <= LLY with LLY >= 1, you can define A as:

 A = max(1, round(LLY/4)) ;

Answer 2

[Kevin]

Thank you for your response Cedric, I have solved my own question. I was calling onto the wrong variable, to define the matrix... silly mistake.