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

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

[Harsh Sharma]

Hi Michael,

This seems like a problem with dataset, can you please share the data ?

[Michael]

Here it is, it is a 900x6 table but I am testing it with only the first bit of data

[Walter Roberson]

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]

I did use readtable and you were right about that being the problem. Thank you!

Answer 1

[Torsten]

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.

[Walter Roberson]

I suspect that Data is a table() object, so you would need

Data_IV_KE = Data{1:100,2};

[Steven Lord]

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

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mean(A)

ans = 1×4

-0.5000 0.2500 0.7500 1.0000

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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);