Excel file reading and writing in MATLAB - Mini Project: Build & Apply

Excel file reading and writing

📖 Scenario: You work in an office where you need to handle sales data stored in Excel files. You want to read this data into MATLAB, process it, and then save the results back to a new Excel file.

🎯 Goal: Learn how to read data from an Excel file, modify it, and write the updated data back to a new Excel file using MATLAB.

📋 What You'll Learn

Read data from an Excel file named sales_data.xlsx

Create a variable to hold the sheet name Sheet1

Calculate the total sales for each product

Write the updated data with total sales to a new Excel file named sales_summary.xlsx

💡 Why This Matters

🌍 Real World

Handling sales or inventory data stored in Excel files is common in many businesses. Automating this with MATLAB saves time and reduces errors.

💼 Career

Data analysts, engineers, and scientists often need to import and export Excel data for reporting and analysis.

1

Read data from Excel file

Write a line of MATLAB code to read the data from the Excel file named sales_data.xlsx into a variable called data.

MATLAB

% Your code here

Hint

Use the readtable function with the filename as a string.

2

Set sheet name variable

Create a variable called sheetName and set it to the string 'Sheet1'.

MATLAB

data = readtable('sales_data.xlsx');
% Your code here

Hint

Assign the string 'Sheet1' to the variable sheetName.

3

Calculate total sales

Add a new column called TotalSales to the data table by multiplying the columns Quantity and Price.

MATLAB

data = readtable('sales_data.xlsx');
sheetName = 'Sheet1';
% Your code here

Hint

Use element-wise multiplication .* to multiply Quantity and Price columns.

4

Write updated data to new Excel file

Write the data table to a new Excel file named sales_summary.xlsx using the sheet name stored in sheetName. Use the writetable function.

MATLAB

data = readtable('sales_data.xlsx');
sheetName = 'Sheet1';
data.TotalSales = data.Quantity .* data.Price;
% Your code here

Hint

Use writetable with the filename, the table, and the sheet name as arguments.

Practice

1. Which MATLAB function is used to read data from an Excel file into a table?

easy

A. csvread

B. xlswrite

C. readtable

D. load

Solution

1. Step 1: Identify the function for reading Excel files

   MATLAB provides readtable to import Excel data as a table.

2. Step 2: Differentiate from other functions

   xlswrite writes data, csvread reads CSV files, and load loads MAT files.

3. Final Answer:

   readtable -> Option C

4. Quick Check:

   Excel read function = readtable [OK]

Hint: Use readtable to import Excel data as tables quickly [OK]

Common Mistakes:

• Confusing readtable with xlswrite
• Using csvread for Excel files
• Trying to use load for Excel data

2. Which of the following is the correct syntax to write a table T to an Excel file named data.xlsx?

easy

A. readtable('data.xlsx', T)

B. write(T, 'data.xlsx')

C. xlsread('data.xlsx', T)

D. writetable(T, 'data.xlsx')

Solution

1. Step 1: Identify the correct function for writing tables

   The function writetable writes tables to Excel files.

2. Step 2: Check the syntax

   The syntax is writetable(T, 'filename.xlsx'). Other options are either reading functions or incorrect.

3. Final Answer:

   writetable(T, 'data.xlsx') -> Option D

4. Quick Check:

   Write table syntax = writetable(T, filename) [OK]

Hint: Use writetable with table and filename to save Excel files [OK]

Common Mistakes:

• Using write instead of writetable
• Confusing xlsread with writing
• Passing table as second argument to readtable

3. What will be the output of the following MATLAB code?

T = readtable('sales.xlsx', 'Sheet', 'Q1', 'Range', 'A1:C5');
disp(height(T));

medium

A. 4

B. 5

C. 3

D. 6

Solution

1. Step 1: Understand the readtable range and header

   The range 'A1:C5' includes 5 rows, but the first row is usually the header.

2. Step 2: Calculate the number of data rows

   Since the first row is header, the data rows are 5 - 1 = 4.

3. Final Answer:

   4 -> Option A

4. Quick Check:

   Rows read minus header = 4 [OK]

Hint: Remember first row is header, so data rows = total rows - 1 [OK]

Common Mistakes:

• Counting header row as data
• Confusing range size with number of rows
• Assuming no header row present

4. Identify the error in this MATLAB code snippet that tries to write a table T to the second sheet of results.xlsx:

writetable(T, 'results.xlsx', 'Sheet', 2, 'Range', 'B2');

medium

A. The 'Sheet' parameter must be a string, not a number

B. The 'Range' parameter cannot be used with writetable

C. The filename must include full path

D. writetable cannot write to Excel files

Solution

1. Step 1: Check the 'Sheet' parameter type

   In writetable, the 'Sheet' argument should be a string with sheet name, not a numeric index.

2. Step 2: Validate other parameters

   'Range' is valid, filename can be relative, and writetable supports Excel files.

3. Final Answer:

   The 'Sheet' parameter must be a string, not a number -> Option A

4. Quick Check:

   Sheet name must be string in writetable [OK]

Hint: Use sheet names as strings, not numbers, in writetable [OK]

Common Mistakes:

• Passing sheet number instead of name
• Thinking Range is invalid for writetable
• Assuming filename needs full path always

5. You want to read only the numeric data from the range B2:D10 in sheet Data of metrics.xlsx into MATLAB as a table. Which code snippet correctly does this and then writes only the first 5 rows back to a new Excel file subset.xlsx?

hard

A. T = readmatrix('metrics.xlsx', 'Sheet', 'Data', 'Range', 'B2:D10');
writetable(T(1:5,:), 'subset.xlsx');

B. T = readtable('metrics.xlsx', 'Sheet', 'Data', 'Range', 'B2:D10');
writetable(T(1:5,:), 'subset.xlsx');

C. T = readtable('metrics.xlsx', 'Sheet', 'Data', 'Range', 'B2:D10');
writetable(T(1:5));

D. T = readmatrix('metrics.xlsx', 'Sheet', 'Data', 'Range', 'B2:D10');
writetable(T, 'subset.xlsx');

Solution

1. Step 1: Read numeric data as a table

   Use readtable with 'Sheet' and 'Range' to get data as a table.

2. Step 2: Write first 5 rows to new Excel file

   Use writetable with T(1:5,:) to write first 5 rows correctly.

3. Final Answer:

   T = readtable('metrics.xlsx', 'Sheet', 'Data', 'Range', 'B2:D10'); writetable(T(1:5,:), 'subset.xlsx'); -> Option B

4. Quick Check:

   readtable + subset rows + writetable = T = readtable('metrics.xlsx', 'Sheet', 'Data', 'Range', 'B2:D10'); writetable(T(1:5,:), 'subset.xlsx'); [OK]

Hint: Use readtable with range, then slice rows before writetable [OK]

Common Mistakes:

• Using readmatrix but then writetable on matrix
• Omitting filename in writetable
• Not slicing rows correctly before writing