Threshold exceedance, where and by how much

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Daphne PARLIARI 2021-6-1

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https://ww2.mathworks.cn/matlabcentral/answers/845325-threshold-exceedance-where-and-by-how-much

评论： Daphne PARLIARI 2021-6-2

采纳的回答： Steven Lord

Ozone.xlsx

Hi guys!

I would love your help on this one:

I have an excel file (see attached) which contains daily values of ozone for three stations (A, B, C). For every day I want to check whether any of these three stations exceed the daily threshold oh 100 μg/m3, which station has exceeded the threshold (if any), and by how many digits.

E.g., 01/01/2006, A, 2 μg/m3

Is there a simple way to do this?

Thanks in advance!!

PS. I'm on Matlab 2019

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Answer 1

Steven Lord 2021-6-1

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https://ww2.mathworks.cn/matlabcentral/answers/845325-threshold-exceedance-where-and-by-how-much#answer_714455

在 MATLAB Online 中打开

Assuming you're reading this data into a table array like this sample one:

load patients
T = table(LastName, Age, Height, Weight);
head(T)
ans = 8×4 table
      LastName      Age    Height    Weight
    ____________    ___    ______    ______

    {'Smith'   }    38       71       176  
    {'Johnson' }    43       69       163  
    {'Williams'}    38       64       131  
    {'Jones'   }    40       67       133  
    {'Brown'   }    49       64       119  
    {'Davis'   }    46       68       142  
    {'Miller'  }    33       64       142  
    {'Wilson'  }    40       68       180  

We can use logical indexing to determine who weighs over 150 pounds.

isOver150 = T.Weight > 150;
patientsOver150 = T(isOver150, :);
head(patientsOver150)
ans = 8×4 table
      LastName      Age    Height    Weight
    ____________    ___    ______    ______

    {'Smith'   }    38       71       176  
    {'Johnson' }    43       69       163  
    {'Wilson'  }    40       68       180  
    {'Moore'   }    28       68       183  
    {'Jackson' }    25       71       174  
    {'White'   }    39       72       202  
    {'Martin'  }    48       71       181  
    {'Thompson'}    32       69       191  

You can see that the first two rows of T are included in patientsOver150 since their weights are 176 and 163 respectively. The next row in patientsOver150 is row 10 of T since rows 3-9 all represent patients with weights under 150. In both cases I'm only showing 10 rows of the tables, which is why the display of patientsOver150 has rows that don't appear in the display of T.

Now to see by how much the patients' weights exceed 150 pounds just compute with that table variable and assign to a new table variable:

patientsOver150.weightOver150 = patientsOver150.Weight - 150;
head(patientsOver150)
ans = 8×5 table
      LastName      Age    Height    Weight    weightOver150
    ____________    ___    ______    ______    _____________

    {'Smith'   }    38       71       176           26      
    {'Johnson' }    43       69       163           13      
    {'Wilson'  }    40       68       180           30      
    {'Moore'   }    28       68       183           33      
    {'Jackson' }    25       71       174           24      
    {'White'   }    39       72       202           52      
    {'Martin'  }    48       71       181           31      
    {'Thompson'}    32       69       191           41      

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Daphne PARLIARI 2021-6-2

Thank you for the help!

The problem is that I have three columns that I want to check for exceedance, and the example works for one. Which means that I can't generate patientsOver150 for my data...

How can I solve this?

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