Matlab Input/Output. Goal of this section Learn user-controlled Input Output Read/write data files (optional) Input/output 5-

Transcription

1 Matlab Input/Output Goal of this section Learn user-controlled Input Output Read/write data files (optional) Input/output 5-1

2 Input: initialization >> a=[ ; 1 1 0] >> b=[1, 2, 3; 2:4] >> b=[1, 2, 3, 2:4] >> b=linspace(3, 5, 5) >> c=[b, 2:4] >> d=[pi, linspace(3, 5, 5)] Input/output 5-2

3 Input: data file >>load a9q1.dat >>% load full_filename (i.e. including.dat) >>% load data to an array named filename Input/output 5-3

4 Input: by command >>grade = input(' key in your lab 5 grade:' ) >>grade = input('key in your lab 5 grade:' ) >>grade = input('key in your lab 5 grade:' ); >>grade = input('key in your lab 5 grade\n' ) % \n: new line >>grades = input(' key in your labs 1-5 grades inside a [ ]:' ) >>% Matlab take the data and assign to variable >>% keyboard input should be sparse, use data files if available Input/output 5-4

5 Output: data file >> save a9q1.dat temp -ASCII >>% save filename array -ASCII Input/output 5-5

6 Printing: text or one matrix Unformatted: disp('text') or disp (matrix) >> disp('pi='), disp(pi) pi= >> a=[1 2 ;3 4]; >> a a = >> disp(a) Input/output 5-6

7 Printing: text and #s in one line Unformatted: disp( ['text', num2str(#)] ) >> disp('pi='), disp(pi) pi= >> disp( ['pi=', num2str(pi)] ) %num2str: number to string pi= >>% text= ['pi=', num2str(pi)], disp(text) % try the following % disp( ['pi=' ; num2str(pi)] ) % disp( ['pi=' num2str(pi)] ) % disp( ['pi=', num2str(pi), ', final answer' ] ) % disp( ['pi=, 2pi=', num2str(pi, 2*pi)] ) % disp( ['pi=', num2str(pi), '2*pi=', num2str(2*pi)] ) % disp( ['pi=', num2str(pi, 2)] ) 7

8 Printing: text and #s in one line Unformatted: disp( ['text', num2str(a row vector)] ) >> a=[ 1 2 3] >> disp(['a=', num2str(a)] ) a=1 2 3 >> a=[ 1; 2; 3] >> disp(['a=', num2str(a)] ) >> disp(['a=', num2str(a')] ) >> a=[ 1 2 3; 4 5 6] >> disp(['a=', num2str(a)] ) Input/output 5-8

9 Printing: text and matrices Formatted: fprintf ('format', list of matrices) >> a a = >> fprintf ('a= %f', a) % Matlab is column dominant a= a= a= a= >> fprintf ('%.2f, %.2f \n',a) 1.00, , 4.00 >> %recycle format by column >> fprintf ('%.2f \t %.2f \n',a') % \t jump to the next tab Input/output 5-9

10 Printing: text and matrices Formatted: fprintf ('format', list of matrices) >> temp=0:20:100; >> tempk= temp tempk = >> table= [temp; tempk] table = >> disp('temp tempk');fprintf('%.2f\t%.2f\n', temp, tempk) temp tempk

11 Printing: text and matrices Formatted: fprintf ('format', list of matrices) Try the following: fprintf('\n %2\t%2', table) fprintf('\n %,2\t%,2', table) fprintf('\n %,2f\t%,2f ', table) fprintf('\n 8.2f%\t%8.2f%', table) fprintf('\n %.2f\t%,2f ', table) fprintf('\n %,2f\t%.2f ', table) fprintf('\n %.2f,\t%.2f ', table) 11

12 Printing: text and matrices Formatted: fprintf ('format', list of matrices) temp=0:20:100; >> tempk= temp tempk = >> table= [temp; tempk] table = >> disp('temp tempk');fprintf('\n %.2f\t%.2f', table) temp tempk

13 Printing: text and matrices To form a table for printing >> table= [temp; tempk] table = >> disp(' temp tempk '),disp (table') temp tempk

14 Printing: text and matrices To form a table for printing >> table1 (:,1)=temp'; >> table1 (:,2)=tempk' table1 = >>disp(' temp tempk '), disp (table1) Input/output 5-14

15 % name % student # % section 51 % Sep 26, 2013 % assignment 3 format compact clear, clc Coding Style (m-file) disp ('name') disp ('student #') disp ('lab51') disp ('assignment 3') disp ('Sep 26, 2013') %a3q1 disp ( ---a3q1---') TC=1:5; TK= TC; Table=[TC' TK ] create a header and modify it each time format compact to save $ clear to clear memory clc to clear command window use disp to print header use blank lines to break program into sections use disp to print a3q1, a3q2 etc

16 Coding Style (M-file) disp(' ') disp('- Paul Paterson -') disp('- SID: ### ### ### -') disp(' ') disp(' Assignment #3 ') disp(' Lab Section 52 ') disp(' Date: Sept. 22, 2010 ') disp(' ') disp(' ') % Question a3q1 - Code disp('question a3q1')

17 syntax fprintf('format_string',argument_list); example fprintf('month=%5d \n',month); output month= example output area= 1 2 Format conversion specification fprintf('area=%9.2f perimeter=%9.4f \n, area,perimeter); perimeter= %w.p: first part of conversion (w) specification is the field width second part (p), if used is the precision (how many decimal places) Input/output 5-17

18 Format complete structure of format specifications for int and float type data %[flag][field width][.precision]type parts in [ ] are optional flags, - left justify, +right justify and add +ve sign if number positive, 0 adds zeros to the left side of the numbers to fill the entire field if needed if flag is not used, the number is right justified if field width is not specified, the field width will automatically be made large enough to accommodate the entire number if precision is not specified, then a default precision (6) will be used regardless of format bank (2), short (5) and long (15) etc. type -d for integer type data -f for float type data -e or E for float type data to be put out in scientific notation almost identical to C refer to Table 7.1 (2e p234, 3e p247) for format specs 18

19 Format everything inside the format string will be used, including space, $, ;,,, etc Examples: fprintf('area=%9.2f perimeter=%9.4f\n',area,perimeter) fprintf('area=%9.2f,perimeter=%9.4f\n',area,perimeter) fprintf('area=%9.2f;perimeter=%9.4f\n',area,perimeter) fprintf('area=%9.2f perimeter=%9.4f\n',area,perimeter) fprintf('cost=$%-9.2f\n',cost) fprintf('cost saving=%-9.2f%%\n',costsaving) Input/output 5-19

20 Line Feed grade = input('key in your lab 4 grade:' ); grade = input('key in your lab 5 grade:' ); disp('line 1'); disp('line 2'); Input/output 5-20

21 Formatting Output how do we control things like line feeds etc. % this will not line feed fprintf('line 1'); fprintf('line 2'); disp('line 3'); % this will line feed fprintf('line 1\n'); fprintf('line 2\n'); disp('line 3\n'); disp('line 4\n'); line 1 line 2 line 3\n line 4\n line 1line 2line Input/output 5-21

22 Formatting Output which one is correct to generate a blank line fprintf('line 1\n\n'); fprintf('line 2\n'); fprintf('line 1\nn'); fprintf('line 2\n'); fprintf('line 1\2n'); fprintf('line 2\n'); fprintf('line 1\n'); fprintf('\n'); fprintf('line 2\n'); fprintf('line 1\n'); disp(' '); fprintf('line 2\n'); Input/output 5-22

23 Formatting Input which one will line feed and where grade = input('key in your lab 4 grade:' ); grade = input('key in your lab 5 grade:' ); grade = input('key in your lab 4 grade:\n' ); grade = input('key in your lab 5 grade:' ); grade = input('key in your lab 4 grade:' ); grade = input('\nkey in your lab 5 grade:' ); Input/output 5-23

24 Formatting Input which one will line/tab feed and where grade = input('key in your lab 4 grade:\t' ); grade = input('key in your lab 4 grade:\n\t'); 00 grade = input('\tkey in your lab 5 grade:' ); Input/output 5-24

25 Write data to a file: syntax file_id=fopen('filename.txt', 'wt' ); % open input file, or create a file id (pointer) fprintf(file_id,'format_string',argument_list); % write to file file_id, note the real file % name is no longer used % number of bytes written (to file) in ans % use fclose (file_id) to close the file Input/output 5-25

26 Write data to a file: example t_ck=fopen('temp_table.txt', 'wt ' ) temp=0:20:100; tempk= temp; table= [temp;tempk] %fprintf('temp tempk'); % this will help you debug %fprintf(t_ck, 'temp tempk'); fprintf('\n %.2f\t%.2f', table) % this will help you debug fprintf(t_ck, '\n %.2f\t%.2f', table) fclose(t_ck); % remember to close all files Input/output 5-26

27 Read data from a file Import Wizard requires interaction with the user, which is extremely undesirable in high level computer programming. Read data from a file by command, syntax [data, fs, up] = xlsread ('filename.xls'); % numeric to data % file string (text) to fs % unprocessed to up [array] = csvread ('filename.txt'); % file has numeric only % values to array Input/output 5-27

28 Write data to a file syntax xlswrite ('filename.xls', array); % write array into filename % as excel worksheet csvwrite ('filename.txt', array); % write array into filename % as comma separated values Input/output 5-28

29 Lessons Learned each input (function) starts a new line (before or after?) can format input with line feed each disp starts a new line (before or after?) can not format disp (unformatted) num2str to convert better to have a table before printing disp easy to use, but only one array at a time fprintf offer control over position and digits, but by column be careful with input/output file format use numbers for now, you will learn how to handle strings in other courses Input/output 5-29

30 Your Tasks Read Chapter 7 Do lab assignment # Input/output 5-30