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Computer Simulation Lab

Electrical and Computer Engineering Department

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“Lecture 11”

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Importing and exporting data

Objectives

• the load and save commands;

• low-level file I/O functions.

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Save Command

SAVE Save workspace variables to disk

SAVE FILENAME saves all variables to binary “filename.mat"

SAVE FILENAME X Y Z saves X, Y, and Z

SAVE ... -ASCII

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Examples

A =[1 2 3 ; 4 5 6]

save myData A

View myData.mat with a text editor

save myData -ascii

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Load Command

load myData

load myData.txt

A=load(‘myData.txt’)

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Low-level file I/O functionsSTART

Write

Open a file with a specific"file_name"for "write"

file handle is created

Type ofOperation

Read

Open a file with a specific"file_name"for "Read"

file handle is created

Write One record to the file(Automatic Pointer Update)

Read One record from the file(Automatic Pointer Update)

End ofOperation

End ofOperation

NoNo

Close THE file

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Low-level file I/O functions

fid = fopen(’marks.bin’, ’w’)

fwrite(fid, name)

fclose(fid)

fread(fid, 78, ’float’);

File Handle

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Low-level file I/O functions

fid = fopen(’marks.bin’, ’w’)

fwrite(fid, name)

Open for Write

Variable Name

Pointer

Update

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Low-level file I/O functions

fid = fopen(’marks.bin’, ’r’)

A=fread(fid, 16, ‘float’)

Open for Read

Variable Size&Type

Pointer

Update

Variable

Name

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Examples

1- Create a binary file named “odd.bin” that contains all the odd numbers between 1 and 99. Examine the file by text editor.

2- Open the binary file and read its contents into an array named OddNums.

3- Append the even numbers between 2 and 100 to the above file. Examine the file by text editor.

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MATLAB Code

fid=fopen('test1.bin','w')

x=[1:2:100];

fwrite(fid,x)

fclose(fid);

fid=fopen('test1.bin','r')

y = fread(fid)

fclose(fid);

fid=fopen('test1.bin','a')x=[2:2:100];fwrite(fid,x)fclose(fid);

fid=fopen('test1.bin','r')y = fread(fid)fclose(fid);

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Example

Create a text file named ‘ASCII.TXT’ that contains all the ASCII characters between 0 and 255. Use a text editor to examine the file.

fid=fopen('ASCII.TXT','w')

x=[1:255];

fwrite(fid,char(x))

fclose(fid);