[andylei]

"column" here refers to a type of data. let's say you have a bunch of records of purchases. one column would be price, another column would be quantity.

if you're doing a linear algebra like transformation, you want to do it on all the prices or all the quantities, and a linear algebra library expects a big array of numbers, which is why you have to transform your records into an array of prices and an array of quantities.

"column" here refers to properties of objects, and not rows vs columns with in an array of number