Read 2*n Data and Write 3*n Data Matlab

MATLAB - Data Import

---

Importing data in MATLAB ways loading data from an external file. The importdata function allows loading diverse information files of unlike formats. It has the following five forms −

Sr.No.	Part & Description
one	A = importdata(filename) Loads information into assortment A from the file denoted by filename.
2	A = importdata('-pastespecial') Loads data from the system clipboard rather than from a file.
3	A = importdata(___, delimiterIn) Interprets delimiterIn equally the column separator in ASCII file, filename, or the clipboard information. Yous can use delimiterIn with any of the input arguments in the in a higher place syntaxes.
iv	A = importdata(___, delimiterIn, headerlinesIn) Loads data from ASCII file, filename, or the clipboard, reading numeric information starting from line headerlinesIn+1.
5	[A, delimiterOut, headerlinesOut] = importdata(___) Returns the detected delimiter graphic symbol for the input ASCII file in delimiterOut and the detected number of header lines in headerlinesOut, using any of the input arguments in the previous syntaxes.

Past default, Octave does not take support for importdata() part, so you will take to search and install this package to make post-obit examples work with your Octave installation.

Case 1

Let u.s. load and display an image file. Create a script file and blazon the following code in it −

filename = 'grin.jpg'; A = importdata(filename); paradigm(A);        

When yous run the file, MATLAB displays the image file. Still, you must store it in the current directory.

Example 2

In this example, nosotros import a text file and specify Delimiter and Column Header. Allow us create a infinite-delimited ASCII file with cavalcade headers, named weeklydata.txt.

Our text file weeklydata.txt looks like this −

SunDay  MonDay  TuesDay  Wed  ThursDay  Friday  SaturDay 95.01   76.21   61.54    twoscore.57       55.79    70.28   81.53 73.11   45.65   79.xix    93.55       75.29    69.87   74.68 60.68   41.85   92.18    91.69       81.32    90.38   74.51 48.sixty   82.14   73.82    41.03       0.99     67.22   93.18 89.13   44.47   57.63    89.36       13.89    19.88   46.60        

Create a script file and type the post-obit code in it −

filename = 'weeklydata.txt'; delimiterIn = ' '; headerlinesIn = 1; A = importdata(filename,delimiterIn,headerlinesIn);  % View data for m = [1:7]    disp(A.colheaders{one, k})    disp(A.data(:, m))    disp(' ') end        

When yous run the file, it displays the following result −

SunDay    95.0100    73.1100    lx.6800    48.6000    89.1300   Monday    76.2100    45.6500    41.8500    82.1400    44.4700   TuesDay    61.5400    79.1900    92.1800    73.8200    57.6300  Midweek    40.5700    93.5500    91.6900    41.0300    89.3600   Thursday    55.7900    75.2900    81.3200    0.9900    xiii.8900   FriDay    seventy.2800    69.8700    90.3800    67.2200    xix.8800  Sat    81.5300    74.6800    74.5100    93.1800    46.6000        

Instance iii

In this example, let us import data from clipboard.

Copy the post-obit lines to the clipboard −

Mathematics is simple

Create a script file and type the following lawmaking −

A = importdata('-pastespecial')        

When you lot run the file, it displays the following result −

A =     'Mathematics is simple'        

Depression-Level File I/O

The importdata function is a loftier-level function. The low-level file I/O functions in MATLAB allow the most command over reading or writing data to a file. Even so, these functions need more detailed information about your file to work efficiently.

MATLAB provides the following functions for read and write operations at the byte or character level −

Function	Description
fclose	Shut i or all open files
feof	Test for end-of-file
ferror	Information nigh file I/O errors
fgetl	Read line from file, removing newline characters
fgets	Read line from file, keeping newline characters
fopen	Open file, or obtain information about open up files
fprintf	Write information to text file
fread	Read data from binary file
frewind	Move file position indicator to beginning of open file
fscanf	Read data from text file
fseek	Motion to specified position in file
ftell	Position in open file
fwrite	Write data to binary file

Import Text Information Files with Low-Level I/O

MATLAB provides the post-obit functions for low-level import of text data files −

• The fscanf office reads formatted data in a text or ASCII file.

• The fgetl and fgets functions read ane line of a file at a time, where a newline character separates each line.

• The fread role reads a stream of information at the byte or bit level.

Example

We take a text data file 'myfile.txt' saved in our working directory. The file stores rainfall data for three months; June, July and August for the year 2012.

The data in myfile.txt contains repeated sets of time, month and rainfall measurements at five places. The header data stores the number of months M; and so nosotros accept M sets of measurements.

The file looks like this −

Rainfall Data Months: June, July, Baronial   M = 3 12:00:00 June-2012 17.21  28.52  39.78  16.55 23.67 nineteen.15  0.35   17.57  NaN   12.01 17.92  28.49  17.twoscore  17.06 11.09 9.59   ix.33   NaN    0.31  0.23  x.46  13.17  NaN    xiv.89 19.33 20.97  19.l  17.65  14.45 xiv.00 18.23  x.34  17.95  xvi.46 nineteen.34 09:10:02 July-2012 12.76  sixteen.94  14.38  xi.86 xvi.89 xx.46  23.17  NaN    24.89 19.33 thirty.97  49.l  47.65  24.45 34.00 18.23  30.34  27.95  16.46 19.34 30.46  33.17  NaN    34.89  29.33 30.97  49.l  47.65  24.45 34.00 28.67  30.34  27.95  36.46 29.34 15:03:40 August-2012 17.09  xvi.55  xix.59  17.25 19.22 17.54  xi.45  13.48  22.55 24.01 NaN    21.19  25.85  25.05 27.21 26.79  24.98  12.23  16.99 eighteen.67 17.54  11.45  13.48  22.55 24.01 NaN    21.19  25.85  25.05 27.21 26.79  24.98  12.23  16.99 18.67        

Nosotros volition import information from this file and display this information. Have the post-obit steps −

• Open up the file with fopen function and become the file identifier.

• Depict the data in the file with format specifiers, such as '%s' for a string, '%d' for an integer, or '%f' for a floating-point number.

• To skip literal characters in the file, include them in the format description. To skip a information field, use an asterisk ('*') in the specifier.

  For example, to read the headers and return the single value for M, we write −

  Thousand = fscanf(fid, '%*s %*s\n%*south %*s %*due south %*s\nM=%d\northward\n', 1);            

• By default, fscanf reads information co-ordinate to our format description until it does not notice any match for the data, or it reaches the end of the file. Hither we will utilize for loop for reading iii sets of information and each time, it will read 7 rows and 5 columns.

• We will create a structure named mydata in the workspace to store data read from the file. This structure has three fields - time, month, and raindata array.

Create a script file and type the following code in it −

filename = '/data/myfile.txt'; rows = vii; cols = 5;   % open up the file fid = fopen(filename);   % read the file headers, find M (number of months) M = fscanf(fid, '%*southward %*s\n%*due south %*due south %*due south %*s\nM=%d\n\n', 1);   % read each set of measurements for northward = i:One thousand    mydata(north).time = fscanf(fid, '%due south', 1);    mydata(due north).calendar month = fscanf(fid, '%southward', ane);      % fscanf fills the array in column order,    % so transpose the results    mydata(north).raindata  = ...       fscanf(fid, '%f', [rows, cols]); end for n = 1:Yard    disp(mydata(n).fourth dimension), disp(mydata(n).month)    disp(mydata(north).raindata) end   % close the file fclose(fid);        

When you lot run the file, it displays the post-obit event −

12:00:00 June-2012    17.2100   17.5700   11.0900   thirteen.1700   fourteen.4500    28.5200       NaN    9.5900       NaN   fourteen.0000    39.7800   12.0100    9.3300   14.8900   18.2300    sixteen.5500   17.9200       NaN   19.3300   ten.3400    23.6700   28.4900    0.3100   20.9700   17.9500    xix.1500   17.4000    0.2300   19.5000   16.4600    0.3500   17.0600   ten.4600   17.6500   19.3400  09:10:02 July-2012    12.7600       NaN   34.0000   33.1700   24.4500    sixteen.9400   24.8900   18.2300       NaN   34.0000    14.3800   19.3300   xxx.3400   34.8900   28.6700    eleven.8600   thirty.9700   27.9500   29.3300   thirty.3400    sixteen.8900   49.5000   16.4600   30.9700   27.9500    20.4600   47.6500   nineteen.3400   49.5000   36.4600    23.1700   24.4500   30.4600   47.6500   29.3400  15:03:40 Baronial-2012    17.0900   thirteen.4800   27.2100   11.4500   25.0500    16.5500   22.5500   26.7900   thirteen.4800   27.2100    nineteen.5900   24.0100   24.9800   22.5500   26.7900    17.2500       NaN   12.2300   24.0100   24.9800    19.2200   21.1900   sixteen.9900       NaN   12.2300    17.5400   25.8500   eighteen.6700   21.1900   16.9900    11.4500   25.0500   17.5400   25.8500   18.6700        

Useful Video Courses

---

Video

Video

Video

Video

Video

Video

kingthiskes.blogspot.com

Source: https://www.tutorialspoint.com/matlab/matlab_data_import.htm

Share this post