Getting around overuse of "if" statements.

Question

Jacob Holmes 2021-7-13

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评论： Rik 2021-7-13

I have a function which takes some data and adds it to an excel file. Depending on the inputs to the function, the data is put in different rows and columns of the excel file. The input is the day, week and site the data was recorded. My code is very clunky and just involves lots of "if" and elseif" statements which make the code hard to read and it takes ages to fix the code if something goes wrong. Is there a better way to write the following code?

function FileLocation(Data,Diff,DAY,SITE,WEEK)
if SITE == 'A'
    if DAY == 'Mon'
        filename = 'daily records.xlsx';
        writematrix(Data,filename,'Sheet',WEEK,'Range','C10:C14')
        filename = 'daily records.xlsx';
        writematrix(Diff,filename,'Sheet',WEEK,'Range','D10:D14')
    elseif DAY == 'Tue'
        filename = 'daily records.xlsx';
        writematrix(Data,filename,'Sheet',WEEK,'Range','E10:E14')
        filename = 'daily records.xlsx';
        writematrix(Diff,filename,'Sheet',WEEK,'Range','F10:F14')
    elseif DAY == 'Wed'
        filename = 'daily records.xlsx';
        writematrix(Data,filename,'Sheet',WEEK,'Range','G10:G14')
        filename = 'daily records.xlsx';
        writematrix(Diff,filename,'Sheet',WEEK,'Range','H10:H14')
    elseif DAY == 'Thu'
        filename = 'daily records.xlsx';
        writematrix(Data,filename,'Sheet',WEEK,'Range','I10:I14')
        filename = 'daily records.xlsx';
        writematrix(Diff,filename,'Sheet',WEEK,'Range','J10:J14')
    else
        filename = 'daily records.xlsx';
        writematrix(Data,filename,'Sheet',WEEK,'Range','K10:K14')
        filename = 'daily records.xlsx';
        writematrix(Diff,filename,'Sheet',WEEK,'Range','L10:L14')
    end
end

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Answer 1

Rik 2021-7-13

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https://ww2.mathworks.cn/matlabcentral/answers/877328-getting-around-overuse-of-if-statements#answer_745558

编辑：Rik 2021-7-13

在 MATLAB Online 中打开

You should use the value of DAY to set the value of a variable you can use as the range. You should also use strcmp to compare char arrays.

In this case you can use ismember:

function FileLocation(Data,Diff,DAY,SITE,WEEK)
if strcmp(SITE,'A')
    filename = 'daily records.xlsx';
    
    days={'Mon','Tue','Wed','Thu','Fri'};
    LookUpTable={...
        'C10:C14','D10:D14';...
        'E10:E14','F10:F14';...
        'G10:G14','H10:H14';...
        'I10:I14','J10:J14';...
        'K10:K14','L10:L14'};
    L=ismember(days,DAY);
    
    %you could check if sum(L) is 1 here if you like
    
    Range=LookUpTable(L,:);
    writematrix(Data,filename,'Sheet',WEEK,'Range',Range{1});
    writematrix(Diff,filename,'Sheet',WEEK,'Range',Range{2});
end

The point is to make sure you are not repeating code. If you have code that you are calling mutliple times, you should either consider a loop or a function. A LUT can also be helpful to avoid repeating code.

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Jacob Holmes 2021-7-13

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This is my solution to it but this solution still has the problem of using if statements. Would it be better to use ismember again with e.g.

site = {'A','B','C'};

and use this to point to the right columns in the look up table?

function ExcelExport(Data,Diff,DAY,SITE,WEEK)
    filename = 'testdata.xlsx'; % Name of the excel document
    
    days={'Mon','Tue','Wed','Thu','Fri'};  % Matrix of week days to later compare
    LookUpTable={...                       %Look up table for row and column destinations for data
        'C10:C14','D10:D14','C16:C20','D16:D20','C22:C26','D22:D26';...
        'E10:E14','F10:F14','E16:E20','F16:F20','E22:E26','F22:F26';...
        'G10:G14','H10:H14','G16:G20','H16:H20','G22:G26','H22:H26';...
        'I10:I14','J10:J14','I16:I20','J16:I20','I22:I26','J22:I26';...
        'K10:K14','L10:L14','K16:K20','L16:L20','K22:K26','L22:L26'};
    L=ismember(days,DAY); % Logical matrix. 0s everywhere apart from where matching day is gives 1
    
    %you could check if sum(L) is 1 here if you like
    if SITE == 'A'
        Range=LookUpTable(L,1:2);
        writematrix(Data,filename,'Sheet',WEEK,'Range',Range{1});
        writematrix(Diff,filename,'Sheet',WEEK,'Range',Range{2});       
    elseif SITE == 'B'
        Range=LookUpTable(L,3:4);
        writematrix(Data,filename,'Sheet',WEEK,'Range',Range{1});
        writematrix(Diff,filename,'Sheet',WEEK,'Range',Range{2});
    else
        Range=LookUpTable(L,5:6);
        writematrix(Data,filename,'Sheet',WEEK,'Range',Range{1});
        writematrix(Diff,filename,'Sheet',WEEK,'Range',Range{2});
    end
end

Jacob Holmes 2021-7-13

在 MATLAB Online 中打开

I've done the following which works and seems quite neat to me:

function ExcelExport(Data,Diff,DAY,SITE,WEEK)
    filename = 'testdata.xlsx'; % Name of the excel document
    
    days={'Mon','Tue','Wed','Thu','Fri'};  % Matrix of week days to later compare
    site = {'A','A','B','B','C','C'};
    LookUpTable={...                       %Look up table for row and column destinations for data
        'C10:C14','D10:D14','C16:C20','D16:D20','C22:C26','D22:D26';...
        'E10:E14','F10:F14','E16:E20','F16:F20','E22:E26','F22:F26';...
        'G10:G14','H10:H14','G16:G20','H16:H20','G22:G26','H22:H26';...
        'I10:I14','J10:J14','I16:I20','J16:I20','I22:I26','J22:I26';...
        'K10:K14','L10:L14','K16:K20','L16:L20','K22:K26','L22:L26'};
    L=ismember(days,DAY); % Logical matrix. 0s everywhere apart from where matching day is gives 1
    S = ismember(site,SITE);
    %you could check if sum(L) is 1 here if you like
    Range=LookUpTable(L,S);
    writematrix(Data,filename,'Sheet',WEEK,'Range',Range{1});
    writematrix(Diff,filename,'Sheet',WEEK,'Range',Range{2});       
end

Rik 2021-7-13

That's fine as well. You need to balance the chance of making a mistake when copy-pasting the LUT with the chance of making a mistake when writing the code that will generate the LUT. Case in point: my initial answer had 'I10:I14','I10:I14' instead of 'I10:I14','J10:J14'.

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Answer 2

Srinik Ramayapally 2021-7-13

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https://ww2.mathworks.cn/matlabcentral/answers/877328-getting-around-overuse-of-if-statements#answer_745548

在 MATLAB Online 中打开

Hey Jacob,

You can always use a switch-case instead of multiple if/else-if statements.

Here in this case, instead of the inner if/else-if statements, i suggest you to replace that code with this

switch DAY
    case 'Mon'
        filename = 'daily records.xlsx';
        writematrix(Data,filename,'Sheet',WEEK,'Range','C10:C14')
        filename = 'daily records.xlsx';
        writematrix(Diff,filename,'Sheet',WEEK,'Range','D10:D14')
    case 'Tue'
        filename = 'daily records.xlsx';
        writematrix(Data,filename,'Sheet',WEEK,'Range','E10:E14')
        filename = 'daily records.xlsx';
        writematrix(Diff,filename,'Sheet',WEEK,'Range','F10:F14')
    case 'Wed'
        filename = 'daily records.xlsx';
        writematrix(Data,filename,'Sheet',WEEK,'Range','G10:G14')
        filename = 'daily records.xlsx';
        writematrix(Diff,filename,'Sheet',WEEK,'Range','H10:H14')
    case 'Thu'
        filename = 'daily records.xlsx';
        writematrix(Data,filename,'Sheet',WEEK,'Range','I10:I14')
        filename = 'daily records.xlsx';
        writematrix(Diff,filename,'Sheet',WEEK,'Range','J10:J14')
    otherwise
       filename = 'daily records.xlsx';
        writematrix(Data,filename,'Sheet',WEEK,'Range','K10:K14')
        filename = 'daily records.xlsx';
        writematrix(Diff,filename,'Sheet',WEEK,'Range','L10:L14')
end

the case element can also accept multiple values like strings, cells etc.

Please refer to the switch,case,otherwise documentation for further reference.

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Jacob Holmes 2021-7-13

Thanks Srinik!

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Answer 3

Max Heiken 2021-7-13

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I agree with Srinik Ramayapally, employing switch is the most obvious change that comes to mind. To extend on that solution, you could factor out the code common to all cases.

switch DAY
    case 'Mon'
        range1 = 'C10:C14';
        range2 = 'D10:D14';
    case 'Tue'
        range1 = 'E10:E14';
        range2 = 'F10:F14';
    case 'Wed'
        range1 = 'G10:G14';
        range2 = 'H10:H14';
    case 'Thu'
        range1 = 'I10:I14';
        range2 = 'J10:J14';
    otherwise
        range1 = 'K10:K14';
        range2 = 'L10:L14';
end
filename = 'daily records.xlsx';
writematrix(Data,filename,'Sheet',WEEK,'Range',range1)
filename = 'daily records.xlsx';
writematrix(Diff,filename,'Sheet',WEEK,'Range',range2)

To completely go without a switch, you could employ a Map object.

range1 = containers.Map({'Mon','Tue','Wed','Thu','Fri'},{'C10:C14','E10:E14','G10:G14','I10:I14','K10:K14'});
range2 = containers.Map({'Mon','Tue','Wed','Thu','Fri'},{'D10:D14','F10:F14','H10:H14','J10:J14','L10:L14'});
filename = 'daily records.xlsx';
writematrix(Data,filename,'Sheet',WEEK,'Range',range1(DAY))
filename = 'daily records.xlsx';
writematrix(Diff,filename,'Sheet',WEEK,'Range',range2(DAY))

But notice that I had to assume here that "otherwise" always means "Fri". You could add more keys into the map that point to 'K10:K14'.

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Jacob Holmes 2021-7-13

Thanks Max. That's a much better way of doing it.

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Getting around overuse of "if" statements.

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