Subject: Re: NSConfused... matrices and NSData

On Sun, Mar 29, 2009 at 12:43 PM, James Maxwell
<jbmaxwell@xxxxxxxxxxxxxxxx> wrote:
> Sorry for the long post, but I'm trying to wrap my head around NSData,
> NSMutableData and matrices.
> So I made an example to test my (mis)conception of how this all should work.

There are two ways to store two-dimensional data in a one-dimensional
array. The standard way is row-major order, in which the rows of the
data are contiguous. To compute the index for this method, you use

The other way is column-major order, which is just the opposite. The
columns are contiguous. Here you compute the index as

You're computing the index as row*rowCount+column, which doesn't work.
As a consequence, you're repeating indexes in your 1D array, which
leads to funny results. Log your computed indexes as well as the
values you find, and I believe the problem will be apparent.


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