René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"proposal to standardize squeezing output from systems","articleBody":"Proposal: When computing frequency and time response output of systems, standardize on indexing first element so output is a 1D array if system is SISO and `squeeze=True`. This is instead of applying `numpy.squeeze` to output. \r\n\r\nCurrently, there are two ways that python-control squeezes output:\r\n\r\n1. __apply 'squeeze' to the output at the end__. This is what functions in `timeresp.py` do, e.g. `forced_response` (edit: and ``iosys`` time responses). An m x n MIMO system (m-output, n-input, m,n\u003e1) produces a [m x n x k] array, where k is the number of data points in time. But a 1 x n system's output gets squeezed to [n x k] and a m x 1 is squeezed to [m x k]. \r\n\r\n2. __use indexing to extract the first element if SISO, otherwise leave a full array__. This is what the frequency response functions `evalfr`, `freqresp` do. If SISO, give [k] length array; MIMO systems always produce [m x n x k] arrays. \r\n\r\nI propose to standardize on the latter: a MIMO system should always output [m x n x k] arrays. Rationale: this facilitates interconnection and keeps indexing the system and its outputs consistent. Along with the proposal: retain the `squeeze=True` keyword argument because it's already in use, but do the 'squeeze' by indexing the first element, and only do it if SISO. \r\n\r\nDocumentation would read something like: \r\n\r\n\"If squeeze is True (default) and sys is single input single output (SISO), returns a 1D array equal to the length k of the input, otherwise returns an (n_outputs, n_inputs, k) array for multiple input multiple output (MIMO) systems.\"\r\n\r\nThis is relevant for #449 and popped up in #442. ","author":{"url":"https://github.com/sawyerbfuller","@type":"Person","name":"sawyerbfuller"},"datePublished":"2020-08-17T17:20:20.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":30},"url":"https://github.com/453/python-control/issues/453"}