{"id":3471,"date":"2018-11-16T04:24:05","date_gmt":"2018-11-16T04:24:05","guid":{"rendered":"https:\/\/www.appservgrid.com\/paw92\/?p=3471"},"modified":"2018-11-17T15:27:51","modified_gmt":"2018-11-17T15:27:51","slug":"getting-started-with-scilab-linux-journal","status":"publish","type":"post","link":"https:\/\/www.appservgrid.com\/paw92\/index.php\/2018\/11\/16\/getting-started-with-scilab-linux-journal\/","title":{"rendered":"Getting Started with Scilab | Linux Journal"},"content":{"rendered":"

Introducing one of the larger scientific lab packages for Linux.<\/em><\/p>\n

Scilab<\/a>
\nis meant to be an overall package for numerical science, along the
\nlines of Maple, Matlab or Mathematica. Although a lot of built-in
\nfunctionality exists for all sorts of scientific computations, Scilab
\nalso includes its own programming language, which allows you to use that functionality
\nto its utmost. If you prefer, you instead can use this language to extend
\nScilab’s functionality into completely new areas of research. Some of
\nthe functionality includes 2D and 3D visualization and optimization tools,
\nas well as statistical functions. Also included in Scilab is Xcos, an
\neditor for
\ndesigning dynamical systems models.<\/p>\n

Several options exist for installing Scilab on your system. Most package
\nmanagement systems should have one or more packages available for
\nScilab, which also will install several support packages. Or, you
\nsimply can download and install a tarball that contains
\neverything you need to be able to run Scilab on your system.<\/p>\n

Once
\nit’s installed, start the GUI version of Scilab with
\nthe scilab command. If you installed Scilab via tarball, this command will
\nbe located in the bin subdirectory where you unpacked the tarball.<\/p>\n

When
\nit first starts, you should see a full workspace created for your
\nproject.<\/p>\n

\"""\"<\/p>\n

Figure 1. When you first start Scilab, you’ll see an empty
\nworkspace ready for you to start a new project.<\/em><\/p>\n

On the left-hand side is a file browser where you can see data
\nfiles and Scilab scripts. The right-hand side has several
\npanes. The top pane is a variable browser, where you can see what
\ncurrently exists within the workspace. The middle pane contains a
\nlist of commands within that workspace, and the bottom pane has
\na news feed of Scilab-related news. The center of the workspace is the
\nactual Scilab console where you can interact with the execution engine.<\/p>\n

Let’s start with some basic mathematics\u2014for example,
\ndivision:<\/p>\n

–> 23\/7
\nans =<\/p>\n

3.2857143<\/p>\n

As you can see, the command prompt is –>, where you enter the
\nnext command to the execution engine. In the variable browser, you
\ncan see a new variable named ans that contains the results of the
\ncalculation.<\/p>\n

Along with basic arithmetic, there is also a number of built-in functions. One thing to be aware of is that these function names are
\ncase-sensitive. For example, the statement sqrt(9) gives the answer
\nof 3, whereas the statement SQRT(9) returns an error.<\/p>\n

There
\nalso are built-in constants for numbers like e or pi. You can use them
\nin statements, like this command to find the sine of pi\/2:<\/p>\n

–> sin(%pi \/ 2)
\nans =<\/p>\n

1.<\/p>\n

If you don’t remember exactly what a function name is, but you remember how
\nit starts, you can use the tab-completion functionality in the Scilab
\nconsole. For example, you can see what functions start with “fa” by
\ntyping those two letters and then pressing the tab key.<\/p>\n

\"""\"<\/p>\n

Figure 2. Use tab-completion to avoid typos while typing
\ncommands in the Scilab console.<\/em><\/p>\n

You can assign variables with the “=” symbol. For example,
\nassign your age to the age variable with:<\/p>\n

–> age = 47
\nage =<\/p>\n

47.<\/p>\n

You then can access this variable directly:<\/p>\n

–> age
\nage =<\/p>\n

47.<\/p>\n

The variable also will be visible in the variable browser pane. Accessing
\nvariables this way basically executes the variable, which is also why you
\ncan
\nget extra output. If you want to see only the value, use
\nthe disp() function, which provides output like the following:<\/p>\n

–> disp(age)<\/p>\n

47.<\/p>\n

Before moving onto more complex ideas, you’ll need to move out of the
\nconsole. The advantage of the console is that statements are executed
\nimmediately. But, that’s also its disadvantage. To write
\nlarger pieces of code, you’ll want to use the included editor. Click
\nthe Applications\u2192SciNotes menu item to open a new window where
\nyou can enter larger programs.<\/p>\n

\"""\"<\/p>\n

Figure 3. The SciNotes application lets you write larger programs
\nand then run them within Scilab as a single unit.<\/em><\/p>\n

Once you’ve finished writing your code, you can run it either by clicking
\nthe run icon on the toolbar or selecting one of the options under the
\nExecute menu item. When you do this, SciNotes will ask you to save
\nyour code to a file, with the file ending “.sce”, before running. Then,
\nit gets the console to run this file with the following command:<\/p>\n

exec(‘\/home\/jbernard\/temp\/scilab-6.0.1\/bin\/test1.sce’, -1)<\/p>\n

If you create or receive a Scilab file outside of Scilab, you can run it
\nyourself using a similar command.<\/p>\n

To build more complex calculations, you also need a way to
\nmake comparisons and loop over several calculations. Comparisons
\ncan be done with either:<\/p>\n

if …. then
\nstmts
\nend<\/p>\n

or:<\/p>\n

if …. then
\nstmts
\nelse
\nstmts
\nend<\/p>\n

or:<\/p>\n

if …. then
\nstmts
\nelseif …. then
\nstmts
\nelse
\nstmts
\nend<\/p>\n

As you can see, the if and elseif lines need to
\nend with then. You can
\nhave as many elseif sections as you need for your particular case. Also,
\nnote that the entire comparison block needs to end with the
\nend statement.<\/p>\n

There
\nalso are two types of looping commands: for loops and
\nwhile loops. As
\nan example, you could use the following to find the square roots
\nof the first 100 numbers:<\/p>\n

for i=1:100
\na = sqrt(i) disp(a)
\nend<\/p>\n

The for loop takes a sequence of numbers, defined by
\nstart:end,
\nand each value is iteratively assigned to the dummy variable i. Then
\nyou have your code block within the for loop and close it with the
\nstatement end.<\/p>\n

The while loop is similar, except it uses a comparison
\nstatement to decide when to exit the loop.<\/p>\n

The last quick item I want to cover is the graphing functionality
\navailable within Scilab. You can create both 2D and 3D graphs,
\nand you can plot data files or the results of
\nfunctions. For example, the following plots the sine function
\nfrom 0 to pi*4:<\/p>\n

t = linspace(0, 4 * %pi, 100) plot(t, sin(t))<\/p>\n

Figure 4. Calling the plot function opens a new viewing
\nwindow where you can see the generated graphs.<\/em><\/p>\n

You can use the linspace command to generate the list of values over
\nwhich the function will be executed. The plot function opens a new
\nwindow to display the resultant graph. Use the commands under
\nthe Edit menu item to change the plot’s details before saving the
\nresults to an image file.<\/p>\n

You can do 3D graphs just as simply. The
\nfollowing plots a parametric curve over 0 to 4*pi:<\/p>\n

t=linspace(0,4*%pi,100); param3d(cos(t),sin(t),t)<\/p>\n

This also opens a new plotting window to display the results. If
\nthe default view isn’t appropriate, click
\nTools\u21922D\/3D Rotation, and with this selected, right-click
\non the graph and rotate it around for a better view of
\nthe result.<\/p>\n

Scilab is a very powerful tool for many types of
\ncomputational science. Since it’s available on Linux, macOS and
\nWindows, it’s a great option if you’re collaborating with other
\npeople across multiple operating systems. It might also prove to be a
\neffective tool to use in teaching environments, giving students
\naccess to a powerful computational platform for no cost, no matter
\nwhat type of computer they are using. I hope this short article has
\nprovided some ideas of how it might be useful to you. I’ve
\nbarely covered the many capabilities available
\nwith Scilab, so be sure to visit the main
\nwebsite<\/a> for a number of good tutorials.<\/p>\n

Source<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

Introducing one of the larger scientific lab packages for Linux. Scilab is meant to be an overall package for numerical science, along the lines of Maple, Matlab or Mathematica. Although a lot of built-in functionality exists for all sorts of scientific computations, Scilab also includes its own programming language, which allows you to use that … <\/p>\n

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