The question is:

"Weight and height measurements of a child taken every month"

Classify this signal as:

  1. one/multidimensional
  2. single/multichannel

I'm not understanding how this can be described as a signal and hence how can it be classified.


I don't feel like it's a very well-posed question, as multi-channel signals are sometimes represented as vector-valued, which would make them multidimensional. However, I assume the answer that is being fished for is:

This is a one-dimensional, two-channel setup. The two channels are the child's height and weight. Each signal is one-dimensional, measured across time. The sample rate of each signal is $1\text{ month}^{-1}$. You could state them mathematically as:

$$ h[n] \equiv \text{ height of child at month } n $$ $$ w[n] \equiv \text{ weight of child at month } n $$

  • $\begingroup$ And what about "a color movie"? I guess It may be 3-dimensional across RGB values, but how many channel? $\endgroup$
    – Sam
    Sep 28 '13 at 16:15
  • 2
    $\begingroup$ You could call a color video as a three-dimensional, three-channel file. The three channels would be the RGB color signals. Each frame is a two-dimensional quantity, while time provides the third dimension. $\endgroup$
    – Jason R
    Sep 28 '13 at 20:52

The dimension is how many coordinated you need to specify a particular measurement. For example, say you had a GPS:

  • GPS speed is 1D
  • GPS ground position is 2D [latitude, longitude]
  • GPS absolute position is 3D [latitude, longitude, height]

The number of channels is how many measurement you make at one time. E.g. if you are taking speed and position measurements then that is multi-channel. But like @JasonR said, depending on how you define the measurements a signal could be multidimensional or multichannel. If operations such as norms or rotations make sense on a set of individual measurements then they should be grouped into a vector (multidimensional) signal.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.