I have a menu in which a user selects a continent and enters in a year that they want to look at a set of data values for. How would I go about extracting the values in matrix

Question

Daniel Jackson 2022-12-14

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1878162-i-have-a-menu-in-which-a-user-selects-a-continent-and-enters-in-a-year-that-they-want-to-look-at-a-s

评论： Voss 2022-12-15

采纳的回答： Voss

Europe.xlsx

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Code for continent and year selection below:

function [continent, con_data] = choose_continent 
%prompt messaged displayed in command window 
disp ('Choose a continent in the menu to view its fossil fuel consumption')
%menu to choose continent 
continent = menu('Choose a contient', 'Africa', 'Asia', 'Europe', 'North America', 'Oceania', 'South and Central America');
%if a continet isn't selceted and menu closed then an error messaged is
%displayed and the menu is reopened
while continent == 0
    disp('Error! Please selected a continent.'); 
    continent = menu('Choose a contient', 'Africa', 'Asia', 'Europe', 'North America', 'Oceania', 'South and Central America');
end
%loads the corresponding data for the chosen continent 
if continent == 1
    continent = 'Africa';
    con_data = xlsread('Africa.xlsx')
elseif continent == 2
    continent = 'Asia';
    con_data = xlsread('Asia.xlsx')
elseif continent == 3
    continent = 'Europe';
    con_data = xlsread('Europe.xlsx')
elseif continent == 4
    continent = 'North America';
    con_data = xlsread('NorthAmerica.xlsx')
elseif continent == 5
    continent = 'Oceania';
    con_data = xlsread('Oceania.xlsx')
elseif continent == 6
    continent = 'South and Central America';
    con_data = xlsread('SouthCentralAmerica.xlsx')
end
function year = choose_year_2
year = input('Enter a year to view: ','s');
if year < 1964
    disp('Error! Please enter a year between 1965 and 2021')
    year = input('Enter a year to view: ','s')
elseif year > 2021
    disp('Error! Please enter a year between 1965 and 2021')
    year = input('Enter a year to view: ','s')
else
    disp('Thank you')
end

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Voss 2022-12-15

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@Daniel Jackson: You don't want to use 's' in the call to input to get the year, since that is numeric:

function year = choose_year_2
year = input('Enter a year to view: ');
if year < 1964
    disp('Error! Please enter a year between 1965 and 2021')
    year = input('Enter a year to view: ')
elseif year > 2021
    disp('Error! Please enter a year between 1965 and 2021')
    year = input('Enter a year to view: ')
else
    disp('Thank you')
end

Also, you should use input in a while loop to get and validate the year, like you do in choose_continent to get and validate the continent.

Voss 2022-12-15

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@Daniel Jackson: Here's a more concise code structure you can use for choose_continent:

function [continent, con_data] = choose_continent()
% prompt messaged displayed in command window 
disp('Choose a continent in the menu to view its fossil fuel consumption');
% menu to choose continent 
all_continents = {'Africa', 'Asia', 'Europe', 'North America', 'Oceania', 'South and Central America'};
while true
    continent = menu('Choose a contient', all_continents{:});
    if continent ~= 0
        break
    end
    % if a continent isn't selected and menu closed then an error messaged is
    % displayed and the menu is reopened
    disp('Error! Please selected a continent.');
end
% store the continent name
continent = all_continents{continent};
% remove ' and ' and then remove ' ' (space) from continent, 
% and append '.xlsx', to get the corresponding file name:
file_name = [strrep(strrep(continent,' and ',''),' ','') '.xlsx'];
% loads the corresponding data for the chosen continent
con_data = xlsread(file_name);

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Answer 1

Voss 2022-12-15

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% user selects continent and year:
[continent, con_data] = choose_continent();
year = choose_year_2();
% then store the row of con_data corresponding to the selected year:
data = con_data(con_data(:,1) == year,:)