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VectorPoints

Status: Experimental

present and registered, but lightly documented and not yet covered by dedicated tests.

Description

VectorPoints

VectorPlot option: integer n specifies an n×n seed grid (default 15). Automatic also uses 15.

Examples (3)

Every input below was run against the current Mathilda build and its output recorded.

Applications (3)

An inert option keyword: it just names the left of a rule

In[1]:= VectorPoints -> 20
Out[1]= VectorPoints -> 20

Protected, with no value of its own

In[2]:= MemberQ[Attributes[VectorPoints], Protected]
Out[2]= True

Accepted by its owning plot builtin

In[3]:= Head[VectorPlot[{-y, x}, {x, -1, 1}, {y, -1, 1}, VectorPoints -> 5]]
Out[3]= Graphics

Implementation notes

Definition. VectorPoints is an inert option keyword for VectorPlot: it gives the integer n specifying an n*n seed grid of arrows (default 15; Automatic also uses 15). It has no builtin and no OwnValue — only the Protected attribute bit is set on the symbol in graphics_init.c, where its docstring also lives. It is a name, not a value, and exists so that VectorPoints -> ... can be written in an option list.

Representation. A bare Protected EXPR_SYMBOL. It never evaluates on its own; it is read as the left-hand side of a VectorPoints -> value rule by the owning plot builtin while it assembles the Graphics[...] result, through the shared options plumbing (OptionValue-style lookup). The value on the right is an ordinary expression and is evaluated as usual — so e.g. a colour name on the right reaches the builtin already reduced to its RGBColor[...] literal.

Usage & limits. Meaningful only inside a call to VectorPlot; elsewhere it is an unused symbol. An unrecognised value is handled (or defaulted) by the owning builtin, not by VectorPoints itself, which carries no logic of its own.

Attributes: Protected.

References

Notes & additional examples

Notes

VectorPoints is an inert option keyword for VectorPlot — an integer n giving an n*n seed grid of arrows (default 15). It has no builtin and no own-value; it is Protected and stays symbolic, read only as the left-hand side of a VectorPoints -> value option rule while the owning builtin builds its Graphics[...] result. The right-hand value evaluates normally before the builtin sees it.