The mean function isn't working and i don't know why

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Michael
Michael 2024-10-7
评论： Michael 2024-10-7
I am trying to take the mean of a data set:
Data_IV_KE = Data(1:100,2);
xbar_IV_KE = mean(Data_IV_KE);
But I keep getting the error message:
Error using sum
Invalid data type. First argument must be numeric or logical.
Error in mean (line 127)
y = sum(x, dim, flag) ./ mysize(x,dim);
Error in Part_B_Exam (line 47)
xbar_IV_KE = mean(Data_IV_KE); % 4m/s
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Walter Roberson
Walter Roberson 2024-10-7
How did you read the csv file in?
I suspect you used readtable() into variable named Data so Data is a table() object, in which case Data(1:100,2) would be a table object not a numeric array.
Michael
Michael 2024-10-7
I did use readtable and you were right about that being the problem. Thank you!

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回答（1 个）

Torsten
Torsten 2024-10-7
编辑：Torsten 2024-10-7
Ran in:
Check whether the data type of Data_IV_KE is "double".
To this end, MATLAB should return "double" when you type
class(Data_IV_KE)
as in
class(5)
ans = 'double'
I suspect it's not.
  2 个评论
Walter Roberson
Walter Roberson 2024-10-7
I suspect that Data is a table() object, so you would need
Data_IV_KE = Data{1:100,2};
Steven Lord
Steven Lord 2024-10-7
Ran in:
Walter, mean on a table array works as of release R2023a, so if your suspicion that Data is a table array is correct the poster must be using a release of MATLAB that's a few years old.
A = gallery('moler', 4) % magic(4) would be boring for this calculation
A = 4×4
1 -1 -1 -1 -1 2 0 0 -1 0 3 1 -1 0 1 4
<mw-icon class=""></mw-icon>
<mw-icon class=""></mw-icon>
mean(A)
ans = 1×4
-0.5000 0.2500 0.7500 1.0000
<mw-icon class=""></mw-icon>
<mw-icon class=""></mw-icon>
mean(array2table(A))
ans = 1x4 table
A1 A2 A3 A4 ____ ____ ____ __ -0.5 0.25 0.75 1
But I agree with you and Torsten, that Data is likely not a double array. Maybe a cell array?
C = num2cell(A)
C = 4x4 cell array
{[ 1]} {[-1]} {[-1]} {[-1]} {[-1]} {[ 2]} {[ 0]} {[ 0]} {[-1]} {[ 0]} {[ 3]} {[ 1]} {[-1]} {[ 0]} {[ 1]} {[ 4]}
mean(C)
Error using sum
Invalid data type. First argument must be numeric or logical.

Error in mean (line 122)
y = sum(x, dim, flag) ./ mysize(x,dim);

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