Reading text files (readtable, textscan) in MATLAB - Mini Project: Build & Apply

Reading Text Files with readtable and textscan in MATLAB

📖 Scenario: You have a text file named students.txt that contains student names and their scores separated by commas. You want to read this data into MATLAB to analyze it.

🎯 Goal: Learn how to read text files using readtable and textscan functions in MATLAB to extract and display student names and scores.

📋 What You'll Learn

Create a text file named students.txt with given content

Use readtable to read the file into a table

Use textscan to read the file into separate variables

Display the student names and scores

💡 Why This Matters

🌍 Real World

Reading data from text files is common when working with exported data from other programs or sensors.

💼 Career

Many jobs require processing data files, and knowing how to read and parse text files is a key skill for data analysis and engineering.

1

Create the text file students.txt

Create a text file named students.txt with these exact lines:
Alice,85
Bob,90
Charlie,78

MATLAB

% Create the file students.txt with the given content
% Your code here

Hint

Use fopen to create the file, fprintf to write lines, and fclose to close the file.

2

Read the file using readtable

Use readtable to read students.txt into a table called studentTable with comma as the delimiter.

MATLAB

fid = fopen('students.txt', 'w');
fprintf(fid, 'Alice,85\nBob,90\nCharlie,78\n');
fclose(fid);
% Read the file into studentTable using readtable
% Your code here

Hint

Use readtable with the 'Delimiter' option set to ','.

3

Read the file using textscan

Open students.txt for reading with fopen. Use textscan with format '%s %d' and delimiter ',' to read names and scores into variables names and scores. Close the file.

MATLAB

fid = fopen('students.txt', 'w');
fprintf(fid, 'Alice,85\nBob,90\nCharlie,78\n');
fclose(fid);
studentTable = readtable('students.txt', 'Delimiter', ',');
% Open file and read with textscan into names and scores
% Your code here

Hint

Use textscan with format '%s %d' and delimiter ','. Remember to close the file.

4

Display the student names and scores

Use a for loop with variable i from 1 to the length of names. Inside the loop, print each student's name and score using fprintf in the format: Name: Alice, Score: 85.

MATLAB

fid = fopen('students.txt', 'w');
fprintf(fid, 'Alice,85\nBob,90\nCharlie,78\n');
fclose(fid);
studentTable = readtable('students.txt', 'Delimiter', ',');
fid = fopen('students.txt', 'r');
data = textscan(fid, '%s %d', 'Delimiter', ',');
names = data{1};
scores = data{2};
fclose(fid);
% Print each student's name and score using a for loop
% Your code here

Hint

Use fprintf inside a for loop to print each name and score.

Practice

1. What is the main advantage of using readtable in MATLAB to read text files?

easy

A. It reads files without opening them first.

B. It requires manual specification of each data type.

C. It only reads numeric data, ignoring text.

D. It automatically loads data into a table with proper formatting.

Solution

1. Step 1: Understand readtable functionality

   readtable is designed to load text files directly into tables, automatically detecting and formatting columns.

2. Step 2: Compare options

   It automatically loads data into a table with proper formatting. correctly describes this automatic loading and formatting. Other options describe incorrect behaviors.

3. Final Answer:

   It automatically loads data into a table with proper formatting. -> Option D

4. Quick Check:

   readtable = automatic table loading [OK]

Hint: Remember: readtable = easy table import [OK]

Common Mistakes:

• Thinking readtable needs manual type input
• Assuming readtable only reads numbers
• Believing files don't need opening before reading

2. Which of the following is the correct syntax to open a text file named data.txt for reading in MATLAB?

easy

A. fileID = fopen('data.txt', 'r');

B. fileID = open('data.txt', 'r');

C. fileID = readfile('data.txt');

D. fileID = textscan('data.txt', 'r');

Solution

1. Step 1: Recall file opening function

   In MATLAB, fopen is used to open files with a mode like 'r' for reading.

2. Step 2: Check each option

   fileID = fopen('data.txt', 'r'); uses fopen correctly. fileID = open('data.txt', 'r'); uses a non-existent open function. fileID = readfile('data.txt'); uses readfile which is not a MATLAB function. fileID = textscan('data.txt', 'r'); misuses textscan which reads from an open file, not opens it.

3. Final Answer:

   fileID = fopen('data.txt', 'r'); -> Option A

4. Quick Check:

   Open file = fopen(filename, 'r') [OK]

Hint: Use fopen to open files before reading [OK]

Common Mistakes:

• Using open instead of fopen
• Trying to read file directly without fopen
• Confusing textscan with fopen

3. Given the following MATLAB code snippet, what will be the output stored in data?

fileID = fopen('numbers.txt', 'r');
data = textscan(fileID, '%d %f');
fclose(fileID);

Assuming numbers.txt contains:

10 3.14
20 2.71
30 1.62

medium

A. A 1x2 cell array with first cell [10;20;30] and second cell [3.14;2.71;1.62]

B. A 3x2 numeric matrix with all numbers

C. A single numeric array combining all values

D. An error because textscan cannot read mixed data

Solution

1. Step 1: Understand textscan output format

   textscan returns a cell array where each cell contains a column of data matching the format specifiers.

2. Step 2: Analyze the format and file content

   Format '%d %f' reads an integer and a float per line. The file has 3 lines, so the first cell will be [10;20;30] and the second cell [3.14;2.71;1.62].

3. Final Answer:

   A 1x2 cell array with first cell [10;20;30] and second cell [3.14;2.71;1.62] -> Option A

4. Quick Check:

   textscan returns cell array columns [OK]

Hint: textscan returns cells, each for one format column [OK]

Common Mistakes:

• Expecting a numeric matrix instead of cell array
• Thinking textscan merges all data into one array
• Assuming textscan cannot read mixed types

4. Consider this MATLAB code snippet:

fileID = fopen('data.txt', 'r');
data = textscan(fileID, '%s %d');

What is the main problem with this code?

medium

A. textscan cannot read strings and integers together.

B. The format specifier '%s %d' is invalid.

C. The file is not closed after reading.

D. fopen should be called with 'w' mode to read.

Solution

1. Step 1: Check file handling steps

   The code opens the file with fopen and reads with textscan, but does not close the file.

2. Step 2: Validate format and usage

   The format '%s %d' is valid for reading a string and an integer. textscan supports mixed types. fopen with 'r' is correct for reading.

3. Final Answer:

   The file is not closed after reading. -> Option C

4. Quick Check:

   Always fclose after fopen [OK]

Hint: Always fclose after reading files [OK]

Common Mistakes:

• Forgetting to close the file
• Thinking '%s %d' is invalid format
• Confusing fopen modes

5. You have a text file records.txt with mixed data: a name (string), age (integer), and height (float) on each line, separated by commas, like:

John,25,5.9
Anna,30,5.5
Mike,22,6.1

Which MATLAB approach correctly reads this file into a table with proper data types?

hard

A. Use readtable('records.txt', 'Delimiter', ',', 'Format', '%s%d%f')

B. Use readtable('records.txt') without specifying delimiter

C. Use textscan(fopen('records.txt', 'r'), '%s %d %f', 'Delimiter', ',') and fclose after

D. Use textscan(fopen('records.txt'), '%s %d %f') without closing file

Solution

1. Step 1: Identify correct reading method for mixed CSV data into table

   readtable automatically detects common delimiters like commas and loads data into a table with inferred types (string for names, double for numbers).

2. Step 2: Compare options

   Use readtable('records.txt') without specifying delimiter: readtable('records.txt') auto-detects comma delimiter. Use readtable('records.txt', 'Delimiter', ',', 'Format', '%s%d%f') uses invalid 'Format' parameter (readtable lacks it). Use textscan(fopen('records.txt', 'r'), '%s %d %f', 'Delimiter', ',') and fclose after: textscan syntax invalid ('Delimiter' not for fid), returns cell array not table. Use textscan(fopen('records.txt'), '%s %d %f') without closing file: textscan fails to parse commas (default whitespace), no fclose.

3. Final Answer:

   Use readtable('records.txt') without specifying delimiter -> Option B

4. Quick Check:

   readtable = auto delimiter + table types [OK]

Hint: readtable auto-detects CSV delimiters into tables [OK]

Common Mistakes:

• Using textscan expecting table output
• Adding invalid 'Format' to readtable
• Omitting delimiter handling in textscan