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Working with your Lemur
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3.4.7. Vector Datacrunching
A vector (also known as an array or list), is a variable that holds more
than one element (number). The Lemur expression syntax allows operations on
vectors and individual access to their elements. You can access the data in certain
Lemur Objects (MultiSlider, MultiBall, Pads, Switches) as vectors. Typically each
“sub object” is an element of a vector. For example, the x coordinates of the
balls in a Multiball object are accessed as
• myball.x[0]
• myball.x[1]
• etc.
Let’s look at some of the operations you can perform on vectors. Assume
we have a MultiSlider object called moo and a MultiBall object called
bar. Below we have listed some expressions involving vectors and the results they
would produce. Assume moo.x contains {0.2 0.3 0.6} and bar.x
contains {0.25 0.5}
• moo.x * 3 Multiply all elements of moo.x by 3, returns {0.6 0.9 1.8}
• moo.x + 2 Add 2 to all elements of moo.x, returns {2.2 2.3 2.6}
• moo.x>0.5 Return a vector consisting of 1 or 0 depending on whether moo.x is
greater than 0.5, returns {0. 0. 1.}
• moo.x + bar.x Add all elements of two vectors. The size of the result is the smaller
of the two input vectors. Returns {0.45 0.8}
• moo.x[0] The first (index 0) element of moo.x, returns 0.2
• bar.x[1] The second element of bar.x, return 0.5
• moo.x[0.5] Interpolated value between bar.x[0] and bar.x[1], returns 0.3
• {moo.x, bar.x} Concatenates moo.x and bar.x, returns {0.2 0.3 0.6 0.25 0.5}
• {moo.x[0],bar.x[1.5]} Creates a new vector consisting of the first element of moo.x
and the average of the second and third elements of bar.x, returns {0.2 0.625}
Please have a look at the Parser Reference for a complete
overview of the possibilities.