SMathStudio.0_85.IOFiles.Article.Eng(1).pdf

Input/Output of data and file manipulation in SMath Studio

Prepared by Gilberto E. Urroz, September 2009

SMath Studio provides functions wfile , rfile, and dfile for output into a file, input from a file, and

deleting an existing file. To illustrate the use of these functions we could start by writing some data to

a file and exploring the contents of the file. Before we do that, however, I want to address an issue

related to the location of the SMath Studio installation folder.

The location of the SMath Studio installation folder

When I first attempted this after installing SMath Studio in my Windows Vista Ultimate 64-bit machine

I kept getting a message indicating that access to the file location was not permitted. This was so

because SMath Studio , by default, sends output to and reads input from the folder /*SMath Studio

Installation Folder*/user/ . In my computer, the *SMath Studio Installation Folder* corresponds to the

directory C:\Program Files(x86)\SMath\SMath Studio\ and it requires Administrator access to modify

its contents. To be able to write data from and read data into SMath Studio , therefore, I copied the

folder C:\Program Files(x86)\SMath\ to a different location. In my case the location chosen was:

C:\Users\Gilberto E. Urroz\Documents\NUMERICAL_APPLICATIONS\SMath

In your computer it could be any location where you don't need Administrator rights to modify content.

I then proceeded to create the folder user , where the data files would reside. Thus, the full address of

this new folder, in my case, is:

C:\Users\Gilberto E. Urroz\Documents\NUMERICAL_APPLICATIONS\SMath\SMath Studio\user

To facilitate access to the program, at this point, I created a new shortcut to SMath Studio in my

desktop. Now we proceed to illustrate the use of the wfile command.

Writing data to a file

You can use function wfile to write a single item of data into a file. Consider the following examples 1 :

You can open the files using, for example, Notepad in a Windows system to check the contents of the

file:

1 I recommend you use only lowercase letters in the filenames used to store data. I had difficulties getting SMath Studio

to read data out of files with uppercase letters in their names.

Thus, you'll need to use the numerical result that you want to write out to a file as the first argument of

wfile . Using the reference to a variable will only write the variable name. The second argument to

wfile is the name of the file, entered without quotes. The file name can only use letters and numbers.

No other characters are allowed in the name of a file.

You can store a range or the resulting vector to a file, e.g.,

The contents of the corresponding files are shown below:

Regarding the notation mat ( 2,4,6,10,12,14,16,18,9,1 ) written in file file04 : this specification contains

the 9 elements of the vector shown as s , above, plus the number of rows ( 9 ) and columns ( 1 ) defining

the vector. Consider, for example, the writing of matrices to files. In the following two examples, the

two matrices have 12 elements, each, but arranged differently. Matrix A has 3 rows and 4 columns,

while matrix B has 3 rows and four columns. They get stored into files file05 and file06 , respectively,

as shown below:

Next, we show the contents of the two files. Notice the specification of rows and columns as the last

two values in the list of data:

Here is another example of using function wfile :

The contents of the file are:

Reading data from a file

To read data from a file use function rfile . The following examples use the files we created above (i.e.,

file01, file02, …, file07 ) to illustrate the use of function rfile . The result from reading data can be

simply shown by using an equal sign(=), or assigned to a variable by using the assignment operator

(:=). Try the following examples:

Additional examples of reading from a file are shown below:

If you attempt to read from a non-existing file you'll get an error message:

Copying a matrix from a spreadsheet

Suppose you have the following 3x3 matrix (only the numbers, no labels, etc.) in an OpenOffice.org

Calc spreadsheet named myMatrix.ods:

Save the file in csv ( c omma- s eparated v alues) format into your user folder in your SMath Studio

installation:

Then, close the newly saved file myMatrix.csv, and open it using Notepad (right-click on the icon, and

select Open with … ):

Plik z chomika:

Inne pliki z tego folderu:

Inne foldery tego chomika: