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Import Data

Import data from a file in the Live Editor

Since R2023a

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Description

The Import Data task lets you interactively import MAT, text, spreadsheet, media (image, audio, and video), and scientific data (HDF5 and netCDF) files. The task automatically generates MATLAB® code for your live script.

Import Data task in the Live Editor

Open the Task

To add the Import Data task to a live script in the MATLAB Editor:

  • On the Live Editor tab, select Task > Import Data.

  • In a code block in the script, type a relevant keyword, such as import, read, or load. Select Import Data from the suggested command completions.

Examples

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Interactively import data from an image file.

Open the Import Data task in the Live Editor. Select the source file and then select the Imported data option in the Display results section to show the image. The task saves the image data in a variable in the workspace. The variable name is based on the name of the source file.

Import Data task

To see the code that this task generates, expand the task display by clicking Show code at the bottom of the task parameter area. 

% Import image
cloudCombined = imread("<path_to_file>\cloudCombined.jpg");

% Display results
imshow(cloudCombined);
title("Image Data From cloudCombined.jpg");

Imported image data showing clouds

Interactively generate reusable MATLAB code to import a Microsoft® Excel® spreadsheet into your workspace. The spreadsheet contains weather data for Boston, Massachusetts, for the month of January 2021. Use the generated code as a template to programmatically import spreadsheets for all twelve months of 2021.

Open the Import Data task in the Live Editor. Enter the filename of the first spreadsheet, 01_weather.xlsx, in the File field.

Import Data task

To see the code that this task generates, expand the task display by clicking Show code at the bottom of the task parameter area.

% Set up the Import Options and import the data
opts = spreadsheetImportOptions("NumVariables", 12);

% Specify sheet and range
opts.Sheet = "3179575";
opts.DataRange = "A2:L32";

% Specify column names and types
opts.VariableNames = ["STATION", "NAME", "LATITUDE", "LONGITUDE", "ELEVATION", "DATE", "AWND", "PRCP", "SNOW", "TAVG", "TMAX", "TMIN"];
opts.VariableTypes = ["categorical", "categorical", "double", "double", "double", "datetime", "double", "double", "double", "double", "double", "double"];

% Specify variable properties
opts = setvaropts(opts, ["STATION", "NAME"], "EmptyFieldRule", "auto");

% Import the data
x01_weather = readtable("<path_to_file>\01_weather.xlsx", opts, "UseExcel", false);

% Clear temporary variables
clear opts

The generated code is separated into steps and documented with comments. Make these changes to automate the process of importing all twelve monthly spreadsheets:

  1. Create a yearWeather table, to which you can append the data from each of the monthly spreadsheets.

  2. Create a namePrefixes vector that contains strings representing each month.

  3. Create a vector of filenames using namePrefixes. Use the regular pattern of the twelve filenames.

  4. Create a vector of data ranges based on the number of days in each month. In the generated code, the range spans columns A to L and rows 2 to 32 (one more than the number of days in January).

  5. Use a for-loop and the variables you created to import all files and append them in yearWeather.

% Changes #1 and #2: Create variables
yearWeather = table();
namePrefixes = ["01" "02" "03" "04" "05" "06" "07" "08" "09" ...
                "10" "11" "12"];

% Set up the Import Options and sheet
opts = spreadsheetImportOptions("NumVariables", 12);
opts.Sheet = "3179575";

% Specify column names and types
opts.VariableNames = ["STATION", "NAME", "LATITUDE", "LONGITUDE", ...
                      "ELEVATION", "DATE", "AWND", "PRCP", "SNOW", ...
                      "TAVG", "TMAX", "TMIN"];
opts.VariableTypes = ["categorical", "categorical", "double", ...
                      "double", "double", "datetime", "double", ...
                      "double", "double", "double", "double", "double"];

% Specify variable properties
opts = setvaropts(opts, ["STATION", "NAME"], "EmptyFieldRule", "auto");

% Changes #3 and #4: Create vectors of filenames and data ranges
fileNames = namePrefixes + "_weather.xlsx";
dataRanges = "A2:L"+string(day(datetime(2021,1,31)+calmonths(0:11))+1);

% Change #5: Import all files and append them in yearWeather
for i = 1:length(namePrefixes)
    fileName = fileNames(i);
    opts.DataRange = dataRanges(i);

    monthWeather = readtable(fileName, opts, "UseExcel", false);
    yearWeather = [yearWeather; monthWeather];
end

% Clear temporary variables
clear opts

Use the imported data to plot the daily low and high temperatures in Boston for each day of 2021.

plot(yearWeather.DATE,[yearWeather.TMIN yearWeather.TMAX])
hold on
xlabel("Date")
ylabel("Temperature (℉)")
legend("Low Temperature","High Temperature",location="Northwest")

Graph of temperatures

Related Examples

Parameters

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Select source

You can enter the path or use the Browse button. The type of the file that you choose to import determines the other parameters in that task that you can select.

When importing a spreadsheet file, select the sheet to import.

Specify imported variable options

When importing a text file or spreadsheet, you can choose the MATLAB data type of the imported data:

  • Table — Data is imported as a MATLAB table. Each column of the data is a variable of the table, and each row of the data is a row of the table. Variable names of the table are derived from column headers of the data.

  • Timetable — Data is imported as a MATLAB timetable. If the first column of the data is not of type datetime or duration, then a new first column of duration values is prepended to the table that starts at 0 s and increments by 1 s for each row of the data.

  • Column vectors — Data is imported as MATLAB column vectors. Each column of the data becomes a column vector, and the name of each column vector variable is derived from the header of the corresponding column of the data.

  • Numeric array — Data is imported as a numeric matrix.

  • String array — Data is imported as a string matrix.

  • Cell array — Data is imported as a cell matrix.

If you select this option, then the task assigns variable names to the imported data using the first row of the file to import. If you do not select this option, then the task assigns default variable names to the imported data and reads the first row of the file to import as data. This parameter is available when importing a text file or spreadsheet as a table or timetable.

If you select this option, then the task preserves the import options in a variable named opts by default. If you do not select this option, then the opts variable is cleared after the import is complete. This parameter is available when importing a text file or spreadsheet.

Display results

Select this option to show the imported data as output of your Live Editor task.

If you select this option, then your import options appear as output of your Live Editor task. If you do not select this option, then the options do not appear. This parameter is available when importing a text file or spreadsheet.

Limitations

  • The Import Data task does not support importing data from HDF5 files that use the Family driver, the Multi driver, or the Split driver. To import data from a file that uses one of these three drivers, use either the MATLAB high-level HDF5 functions (for example, h5read or h5readatt) or the MATLAB low-level HDF5 functions.

Version History

Introduced in R2023a

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See Also

Functions

Objects

Apps