Understanding parameters sent to Matlab quiver function

From the documentation, I saw that Color parameter can be passed to the quiver function as either

'Color', 'k'

or just

'k'

If came across some alternate calls to the quiver function:

quiver(longitude, latitude, u, v, 'Color', 'k');
quiver(longitude, latitude, u, v, 0.5, 'k');
quiver(longitude, latitude, u, v, 0, 'k');

From the documentation, I understood parameters till u,v. After running the code, I see that call with 0.5 as parameter results in arrows that are bit more dispersed than first call. Call with 0 as parameter results in just dots (no arrows).

Can someone please explain how the 0 or 0.5 params are being interpreted by the quiver function?

MATLAB documentation typically shows the different ways of calling functions, and explicitly explains each input. In your example you are using two different ways of calling quiver per the documentation:

https://uk.mathworks.com/help/matlab/ref/quiver.html

All options (as of 24a)

quiver(X,Y,U,V)
quiver(U,V)
quiver(___,scale)
quiver(___,LineSpec)
quiver(___,LineSpec,'filled')
quiver(___,Name,Value)

Where ___ means you can use any of the previous syntaxes, plus the input being described. So you are specifically asking about the two variants

1. quiver(X,Y,U,V,scale,LineSpec), where scale is 0 or 0.5, and LineSpec is 'k' (a black line). The scale and line spec options have their own detailed docs on the same page

   e.g. your quiver(longitude, latitude, u, v, 0.5, 'k');

https://uk.mathworks.com/help/matlab/ref/quiver.html#mw_fe38877d-5343-48ab-aa8f-87ffbcb85fe4 scale - Arrow scaling factor, specified as a nonnegative number or 'off' [...]

https://uk.mathworks.com/help/matlab/ref/quiver.html#mw_b668e255-e1d3-40c8-a5cd-e426dd74c0ff LineSpec - Line style, marker, and color, specified as a character vector or string containing symbols [...]

2. quiver(X,Y,U,V,Name,Value) where you're providing one name-value pair which is the color

   e.g. your quiver(longitude, latitude, u, v, 'Color', 'k');

https://uk.mathworks.com/help/matlab/ref/quiver.html#namevaluepairarguments

[...] Before R2021a, use commas to separate each name and value, and enclose Name in quotes.

Example: 'Color','r','LineWidth',1 [...]