A quick introduction to Scilab

A quick introduction to Scilab Tutorial on Risk Management, WS 2013/14

Outline

Scilab environment

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two windows: console and editor

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console: type commands directly (history and ↑-key)

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editor: type (longer) commands, save and execute them

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help-files: description and examples of commands

Basic elements of the language

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real variables and basic mathematical operations

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matrices I I I I

creation of matrices ([], ones, zeros) access to matrices ((3,4), :, $) basic operations (+, -, *, ’) element-wise operations (.)

Basic elements of the language (continued)

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branching and looping I if, elseif, else I for

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functions I I

definition of a function multiple input and output arguments

Writing good code

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Choose meaningful names for variables and functions.

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Use indentation for a better overview.

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Avoid hard-coded constants, but use variables instead. (length)

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Is your for loop necessary? Employ vectorization.

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Whenever you write code of the same pattern twice, define a function.

Avoiding and finding errors Avoiding errors I

Be sure to know exactly what your command does (if not, try it on the command line).

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Proceed step by step. Test after every step.

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Always close a bracket at the same time you open it.

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Use variables as arguments to test your function.

Finding errors (debugging) I

If the real input is long, use a short example for testing.

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pause command (resume, abort)

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variable browser

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plausibility tests: special cases, extreme values, monotonicity

Stixbox

Installation of the the Scilab module Stixbox I

search for available modules: atomsSearch("stixbox")

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install stixbox: atomsInstall("stixbox")

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restart Scilab or use atomsLoad("stixbox")

Why do we need Stixbox? I

statistics toolbox: distribution functions, statistical tests, plotting facilities, etc.

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we can use a lot of commands without implementation