Should it be "height and width" or "width and height" when talking about matrix and sentence?

[hfridholm]

The datatypes matrix and sentence are two-dimensional arrays, therefor you can think of them as a coordinate system. To access a slot in this field, you need to have two indexes, one for which array, and the other for which item. Should the indexes be: first the array-index, then the slot-index ("height and width")? Or should it be: first the x-index, then the y-index, like in a coordinate system ("width and height")? If you know what you would take, comment the explanation of your thought.