How to loop through table column comparing subsequent records but ignoring zero values?

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Diane
Diane 2023-5-12
回答： Divyanshu 2023-5-16
I would like to ensure subsequent column values (of wind power) only change by 20% per time step, except where there is a zero value. That is, [1am 2am 3am 4am 5am] [100, 200, 250, 0, 100] would become [1am 2am 3am 4am 5am] [100, 120, 144, 0, 100]. However, as soon as the loop reaches a zero, the rest of the column is set to zero, because 20% of zero is zero.
Here is the code I have tried. I just keep getting a list of zeros after reaching the first zero. I think I need logical indexing but can’t work out how to implement it in this instance.
Thank you for all suggestions.
WeatherT2 = readtable('C:\Windyield_data.csv','Delimiter','comma');
head(WeatherT2)
% WeatherT2 is table name.
% WeatherT2.timestamp and WeatherT2.windpower are the column names.
----------------------------------
numRows = height(WeatherT2)
for row = 2 : numRows
if WeatherT2.windpower(row) == 0
WeatherT2.windpower(row+1) = WeatherT2.windpower(row+1);
elseif WeatherT2.windpower(row) > WeatherT2.windpower(row-1)*1.2
WeatherT2.windpower(row) = WeatherT2.windpower(row-1)*1.2;
else WeatherT2.windpower(row) <= WeatherT2.windpower(row-1)*1.2
WeatherT2.windpower(row) = WeatherT2.windpower(row);
end
end
----------------------------------
numRows = height(WeatherT2)
for row = 2 : numRows
if WeatherT2.windpower(row) > 0
if WeatherT2.windpower(row) > WeatherT2.windpower(row-1)*1.2
WeatherT2.windpower(row) = WeatherT2.windpower(row-1)*1.2;
end
end
end
----------------------------------
numRows = height(WeatherT2)
for row = 2 : numRows
while WeatherT2.windpower(row) ~= 0
if WeatherT2.windpower(row) > WeatherT2.windpower(row-1)*1.2
WeatherT2.windpower(row) = WeatherT2.windpower(row-1)*1.2;
end
break
end
end
----------------------------------
numRows = height(WeatherT2)
for row = 2 : numRows
if WeatherT2.windpower(row) > WeatherT2.windpower(row-1)*1.2
WeatherT2.windpower(row) = WeatherT2.windpower(row-1)*1.2;
else
WeatherT2.windpower(row) =0
break
end
end
----------------------------------
skipNum = [WeatherT2.windpower ~= 0];
numRows = height(WeatherT2)
for row = 2 : numRows
if ismember(row,skipNum) %if row is member of the skipNum array
if WeatherT2.windpower(row) > WeatherT2.windpower(row-1)*1.2
WeatherT2.windpower(row) = WeatherT2.windpower(row-1)*1.2;
end
end
end

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采纳的回答

Divyanshu
Divyanshu 2023-5-16
Hi Diane,
According to the description provided, here are few assumptions that I have made:
  • If current value is 0 in the column, then the subsequent value should not be changed.
  • In each iteration the new value of current row is 120% of the previous row value and has nothing to do with the old value of current row.
Here is a demo script you can refer to, and feel free to modify it according to your use case:
windpower = [100 200 250 0 80 130 150]';
iszero = windpower == 0;
numRows = height(windpower);
for i=2:numRows
if(~iszero(i-1))
if(~iszero(i))
windpower(i) = windpower(i-1)*1.2;
end
end
end

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