load and if conditions

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mcm 2016-10-19

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评论： Walter Roberson 2016-10-19

I need a for loop that will call a data set (1997 or 2013) and pull data from the data to calculate what each value if equal 2. The code I created doesn't run. But this is what I have so far. How can I improve it?

pick_year = input('Pick a year: either 1997 or 2013: ')
for pick_year
    if pick_year == 1997
        load('UPDRSscores_1997')
    elseif pick_year == 2013
        load('UPDRSscores_2013')
    end
   if pick_year == 0 
        display('normal')
    elseif pick_year == 1 
        display('slight')
    elseif pick_year == 2
        display('mild')
    elseif pick_year == 3
        display('moderate')
    elseif pick_year == 4
        display('severe')
   end
end

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James Tursa 2016-10-19

is pick_year actually one of the variables that gets loaded?

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Answer 1

James Tursa 2016-10-19

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Maybe just get rid of that for-loop (assuming pick_year is one of the variables that gets loaded). E.g.,

pick_year = input('Pick a year: either 1997 or 2013: ')
    if pick_year == 1997
        load('UPDRSscores_1997')
    elseif pick_year == 2013
        load('UPDRSscores_2013')
    else
        error('Invalid year')
    end
   if pick_year == 0 
        display('normal')
    elseif pick_year == 1 
        display('slight')
    elseif pick_year == 2
        display('mild')
    elseif pick_year == 3
        display('moderate')
    elseif pick_year == 4
        display('severe')
   end

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Answer 2

Walter Roberson 2016-10-19

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"poofing" a variable value from a load() can have different results with different MATLAB versions. Earlier it was well defined, but it is getting increasingly restricted. It is recommended that you always use load() with an output variable and pull the data out of the output variable.

pick_year = input('Pick a year: either 1997 or 2013: ')
filename = sprintf('UPDRSscores_%d.mat', pick_year);
if ~exist(filename, 'file')
  error('file "%s" does not exist', filename);
end
datastruct = load(filename);
pick_year = datastruct.pick_year;   %pull it out of what was loaded from the file
   switch pick_year
     case 0:
        display('normal')
     case 1:
        display('slight')
     case 2:
        display('mild')
     case 3:
        display('moderate')
     case 4:
        display('severe')
     otherwise:
        error('stored pick_year had bad value %f\n', pick_year);
  end

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mcm 2016-10-19

The code you just wrote, does not work. How can I improve it. There is a problem with this line pick_year = datastruct.pick_year; %pull it out of what was loaded from the file

how should i change it?

Walter Roberson 2016-10-19

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pick_year = input('Pick a year: either 1997 or 2013: ')
filename = sprintf('UPDRSscores_%d.mat', pick_year);
if ~exist(filename, 'file')
  error('file "%s" does not exist', filename);
end
datastruct = load(filename);
pick_year = datastruct.pick_year;   %pull it out of what was loaded from the file
if pick_year == 0
      display('normal')
elseif pick_year == 1
      display('slight')
elseif pick_year == 2
      display('mild')
elseif pick_year == 3
      display('moderate')
elseif pick_year == 4
      display('severe')
else
      error('stored pick_year had bad value %f\n', pick_year);
end

Or, better:

states = {'normal', 'slight', 'mild', 'moderate', 'severe'};
pick_year = input('Pick a year: either 1997 or 2013: ')
filename = sprintf('UPDRSscores_%d.mat', pick_year);
if ~exist(filename, 'file')
  error('file "%s" does not exist', filename);
end
datastruct = load(filename);
pick_year = datastruct.pick_year;   %pull it out of what was loaded from the file
if pick_year >= 0 && pick_year <= length(states) - 1 && mod(pick_year,1) == 0
   display( states{pick_year + 1} );
else
   error('stored pick_year had bad value %f\n', pick_year);
end