File Operations in Matlab

1
File Operations in Matlab

• Load / Save
• .dat, .mat vs. -ascii
• fopen /fclose

2
Load and Save

• gtgt x 110
• x
• 1 2 3 4 5 6 7 8
  9 10
• gtgt y x . 2
• y
• 1 4 9 16 25 36 49 64
  81 100
• gtgt save x.mat x y
• gtgt load x.mat

• Get data from other applications
• Save variables for later use

3
-ascii option

• Save variable data into file with standard
  character format
• Open or import into spreadsheets, database, word
  processor

• gtgt x
• x
• 1 2 3 4 5 6 7 8
  9 10
• gtgt y
• y
• 1 4 9 16 25 36 49 64
  81 100
• gtgt save x.txt x y -ascii
• gtgt

4
fopen / fclose

• Open files and write or read data into them.
• Use the file ID to specfiy placement of data.
• fprintf writes formatted data to files

• gtgt fid fopen('x.mat', 'w')
• gtgt load x.txt
• gtgt fprintf(3, ' 6.4f\n ', x)
• gtgt fid
• fid
• 3
• gtgt fclose(fid)
• gtgt

5
results
x.txt
x.mat
6
Hints

• 5.18 Use example 4.7 (p.166)
• Turn this into a function
• function slope, y_int lsqfit(x,y)
• Functions section 5.1 (p. 190)

7
Hints

• 5.22
• Use rand function to generate random number.
• Scale from 0,1) interval to -1,1)
• Make user-defined function to transform uniform
  to normal
• use this function in m-file to generate array
• use hist() function, and std() built in functions

8
Hints

• 7.6 structure arrays
• Define structure array in m-file
• Create user defined function that
• accepts structure array
• plots the info in the array
• section 7.3.4-5 (p. 310 -311)