how can I write a function

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Manav Divekar 2021-11-17

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评论： Dave B 2021-11-18

i have a data base with name gender and age not necessarily in the same order, some data base is gender name age. for example

'name' 'gender' 'age'

'mary' 'f' 25

'john' 'm' 35

'anna' 'f' 30

'paul' 'm' 22

'elaina' 'f' 38

if i have to use this database as cell array and only get the names of male how i do so?

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Answer 1

Dave B 2021-11-17

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编辑：Dave B 2021-11-17

在 MATLAB Online 中打开

Your data look similar to this (as you've described them):

load patients
data=[{'name'} {'gender'} {'age'}; LastName Gender num2cell(Age)]

You just use strcmp to compare strings, and specify you want the rows where gender contains 'm' and column 1

data(strcmp(data(:,2),'Male'),1) % obviously you'll use 'm' in your case
ans = 47×1 cell array
    {'Smith'    }
    {'Johnson'  }
    {'Wilson'   }
    {'Moore'    }
    {'Jackson'  }
    {'White'    }
    {'Martin'   }
    {'Thompson' }
    {'Martinez' }
    {'Robinson' }
    {'Hall'     }
    {'Hernandez'}
    {'King'     }
    {'Scott'    }
    {'Green'    }
    {'Baker'    }
    {'Nelson'   }
    {'Mitchell' }
    {'Perez'    }
    {'Roberts'  }
    {'Turner'   }
    {'Phillips' }
    {'Parker'   }
    {'Edwards'  }
    {'Collins'  }
    {'Stewart'  }
    {'Reed'     }
    {'Bell'     }
    {'Murphy'   }
    {'Ward'     }

If it were me, I'd put these in a table and use strings, it's so much better!

t=array2table(data(2:end,:),'VariableNames',data(1,:));
t.name=string(t.name);
t.gender=categorical(t.gender);
t.age=cell2mat(t.age);
t.name(t.gender=="Male")
ans = 47×1 string array
    "Smith"
    "Johnson"
    "Wilson"
    "Moore"
    "Jackson"
    "White"
    "Martin"
    "Thompson"
    "Martinez"
    "Robinson"
    "Hall"
    "Hernandez"
    "King"
    "Scott"
    "Green"
    "Baker"
    "Nelson"
    "Mitchell"
    "Perez"
    "Roberts"
    "Turner"
    "Phillips"
    "Parker"
    "Edwards"
    "Collins"
    "Stewart"
    "Reed"
    "Bell"
    "Murphy"
    "Ward"

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Dave B 2021-11-17

编辑：Dave B 2021-11-18

在 MATLAB Online 中打开

Re how to generalize, this is why using a table makes more sense, because then you can refer to a variable name instead of a number. However you could look at the first row with the same principal

load patients
data=[{'name'} {'gender'} {'age'}; LastName Gender num2cell(Age)];
col = strcmp(data(1,:),'gender');
data(strcmp(data(:,col),'Male'),1) 
ans = 47×1 cell array
    {'Smith'    }
    {'Johnson'  }
    {'Wilson'   }
    {'Moore'    }
    {'Jackson'  }
    {'White'    }
    {'Martin'   }
    {'Thompson' }
    {'Martinez' }
    {'Robinson' }
    {'Hall'     }
    {'Hernandez'}
    {'King'     }
    {'Scott'    }
    {'Green'    }
    {'Baker'    }
    {'Nelson'   }
    {'Mitchell' }
    {'Perez'    }
    {'Roberts'  }
    {'Turner'   }
    {'Phillips' }
    {'Parker'   }
    {'Edwards'  }
    {'Collins'  }
    {'Stewart'  }
    {'Reed'     }
    {'Bell'     }
    {'Murphy'   }
    {'Ward'     }

Re how to apply to age

this approach won't work, 'age' can't be compared to 30.
strcmp just compares strings, it's not useful for numbers.
=< is not a matlab operation
If age a cell, you'll have to convert it to a matrix, and then it'll be off by one row because of the headings.
Really just use a table, your life will be much easier!