Can't calculate mean of dataset (single column), "[F]irst argument must be numeric or logical"

I am currently trying to determine the mean, median, and mode of a given dataset.

Right now, the data is in what I believe to be a string. There should be no text in said strings, only numeric data.

The dataset in question is a "string" that has only one column full of data.

I wish to, as a start, determine the mean.

When I attempt to do so, I get this error.

M = mean(Dataset)
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);

I checked using

tf = istable 

That the dataset was not a table.

May someone provide guidance as to what I am doing wrong? If I need to convert the dataset, how and to what?

Thanks.

[dpb]

The above definitely shows an array of string arrays -- we need to see what the actual data file looks like -- and how you brought it into MATLAB. importdata sometimes does funky things...

Attach the data file with the paperclip icon...

[Austin Davis]

Here is the data file. I brought it in by importing an Excel spreadsheet (Import Data) as an array, and generating a subset of that data via randsample.

[dpb]

fn=websave('Dataset.mat','https://www.mathworks.com/matlabcentral/answers/uploaded_files/1133605/Dataset.mat')

fn = '/users/mss.system.E3SzLl/Dataset.mat'

load(fn)
whos

  Name           Size            Bytes  Class     Attributes

  Dataset      551x1             29850  string              
  cmdout         1x33               66  char                
  fn             1x36               72  char                

Dataset(1:10)

ans = 10×1 string array
    "60045"
    "12491"
    "56553"
    "203401"
    "1706"
    "1893"
    "6332"
    "2638882"
    "349520"
    "1483"

Dataset=str2double(Dataset);
Dataset(1:5)

ans = 5×1

60045 12491 56553 203401 1706

mean(Dataset)

ans = 1.4480e+05

But, we need to see the actual code used to read in the Excel file as to why it was imported as string array instead of numeric -- attaching the beginning if not all of the Excel file itself would be the best way to see what went wrong if it is something to do with the file itself.

Simply

data=readmatrix('YourFile.xlsx');

would normally be "the right stuff"...

[Austin Davis]

I don't have the code, as I imported it directly as a string array, because without this, I was not able to properly plot or subplot via histfit in table format. As such, I imported everything as a string array, and presumably taking a subset of that dataset (the one which I have sent right now) continued to be a string array.

So I would just have to convert back using str2double again?

Thank you.

[dpb]

There should be no need for any such machinations with strings...if you imported as a MATLAB table, then the problem probably had to do with not using the variables within the table but trying to reference the table itself.

Again, attach a piece of the Excel file itself and tell us what you're trying to do -- we can't see your terminal from here and can't debug what we can't see...it is possible that sometimes a spreadsheet file can be save such as it does lead to confusion as to data types -- not terribly often, but can/does happen. Or, there are other fields in the file that don't match up -- all kinds of superfluous stuff is occasionally stuffed into a spreadsheet for auxiliary data or explanation or whatever.

[Walter Roberson]

Your reasoning does not make sense. You would not be able to take the string array and "properly plot of subplot via histfit in table format" with the string array.

You should either readmatrix() or readtable(), and if you use readtable() then use variable-name or column references as appropriate when calling functions.

Answer 1

[Pravarthana P]

Hi Austin Davis,

I understand that you are facing an issue while calculating the mean of a given dataset in ‘string’ datatype.

In order to use the ‘mean’ function the input should be in any one of the mentioned data types in this documentation link.The dataset can be converted to the required data type using "str2double" function, following which,- the mean can be calculated.

For further information kindly refer to the following documentation links:

Average or mean value of array - MATLAB mean (mathworks.com)

Convert Text to Numeric Values - MATLAB & Simulink (mathworks.com)

I hope this information helps you!