Is X a vector that has 1 one for the direction that we are interested in and 0 for the others?

@rilakkuma X is arbitrary and only represents one direction. If you mean something like (0,0,...,1,...,0), it doesn't have to be like this.

Is X a vector that has 1 one for the direction that we are interested in and 0 for the others?

@rilakkuma X is arbitrary and only represents one direction. If you mean something like (0,0,...,1,...,0), it doesn't have to be like this.