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I am looking for a symbol to represent the operation of taking unique values from a vector. So, say the symbol was $\theta$:

$v = [0, 0, 0, 1, 1, 1, 3, 1, 2, 0]$

$\theta(v) = [0, 1, 3, 2]$

Or is this something that just isn't defined?

Thanks

EDIT

Thanks all for your help here. Your answers and comments have led me to realise that doing this operation on a vector is not really what I want to do; using a set makes much more sense logically.

(Background: I have many coordinates $\boldsymbol{p}_i = [x_i, y_i, z_i]$ in 3D space, which I then perform a rounding function on so they are equally sampled. However, there will be many duplicates points at each new coordinate, so I remove the duplicated $\boldsymbol{p}$ points to get the final set of points. So it makes sense to define a set $\boldsymbol{P} = \{\boldsymbol{p}_1, ... \boldsymbol{p}_i, \cdot \boldsymbol{p}_n\}$).

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    @Gunnar Magnusson: I do not think that the OP wants to consider the usual coordinate projection onto a coordinate subspace.2010-12-20

2 Answers 2

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A common way to express that you are throwing away duplicates is to translate a sequence into a set. A set is commonly understood as an unordered collection of distinct objects. It is usually denoted using curly braces. So you could write $\theta(v) = \{v_i\}_{i\in\{1,\ldots,n\}}$, where $v=[v_1,\ldots,v_n]$.

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    @Bill Yes, that's right.2010-12-20
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There is no standard notation for the set of coefficients of a vector. Indeed, there's not even any standard notation for the set of coefficients of a polynomial (which would be useful when taking the content, i.e. the gcd / ideal generated by the coefficients).