MATLAB: Operator ‘-‘ is not supported for operands of type ‘table’.

tabletabletoarray

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Assuming that data is your table, then you need to use the correct type of indexing:

() parenthese returns a sub-table of the table.
{} curly braces returns the contents of the table.

So you need to use curly braces if you want to use the numeric data stored in the table:

100 * 4 * ((data{2:end,4} - data{1:end-1,4} ) ./  data{1:end-1,4});
%               ^       ^       ^         ^           ^         ^

The different types of indexing are explained in the MATLAB documentation:

https://www.mathworks.com/help/matlab/matlab_prog/access-data-in-a-table.html

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MATLAB: How to extract the contents of an HTML table on a web page into a MATLAB table

You can extract the <table> content, which is all stored in a set of <td> tags, as a string array and go from there.

You first need to use findElement and extractHTMLText on an htmlTree object.

You then can use reshape to arrange the data, then use array2table to convert to a table.

Here is one approach:

travel_data = webread('https://www.tsa.gov/coronavirus/passenger-throughput');
travel_data_tree = htmlTree(travel_data);
selector = "td";
subtrees = findElement(travel_data_tree,selector);
str = extractHTMLText(subtrees);
table_data = str(4:end); % first three elements are just the column names
reshape_ncols = 3;
reshape_nrows = length(table_data)/reshape_ncols;
table_data_reshaped = reshape(table_data,reshape_ncols,reshape_nrows)';
% Convert to table
traveler_data_table = array2table(table_data_reshaped,'VariableNames',["Date" "Travelers_Today" "Travelers_Last_Year"]); % I got lazy with VariableNames, I know.
% Convert data types from strings to appropriate types
traveler_data_table.Date = datetime(traveler_data_table.Date);
traveler_data_table.Travelers_Today = str2double(traveler_data_table.Travelers_Today);
traveler_data_table.Travelers_Last_Year = str2double(traveler_data_table.Travelers_Last_Year);
traveler_data_table.Traveler_Ratio = traveler_data_table.Travelers_Today ./ traveler_data_table.Travelers_Last_Year;
% Plot the results
figure
plot(traveler_data_table.Date,traveler_data_table.Traveler_Ratio)
title("TSA Traveler Ratio by Date (2020 vs. 2019)")
grid on
% Some more fun analysis
% When did it bottom out?
[min_ratio,idx] = min(traveler_data_table.Traveler_Ratio);
min_ratio_pct = 100*min_ratio;
min_date = traveler_data_table.Date(idx);
disp("The minimum traveler ratio of " + min_ratio_pct + "% occurred on " + string(min_date))
latest_pct = 100*traveler_data_table.Traveler_Ratio(1);
disp("The current ratio is " + latest_pct + "%")

MATLAB: How to close a web browser in MATLAB 7.5 (R2007b)

This command will close the web browser that has been opened with the WEB function in MATLAB 7.5 (R2007b):

web www.mathworks.com
com.mathworks.mlservices.MatlabDesktopServices.getDesktop.closeGroup('Web Browser')

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Related Solutions

MATLAB: How to extract the contents of an HTML table on a web page into a MATLAB table

MATLAB: How to close a web browser in MATLAB 7.5 (R2007b)

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