converting a table of numeric data into a double array?

Hi,

I am trying to convert a table of numeric data to a double array using some of the methods presented before in some answers to similar questions like:

1- table2array function

2- X{:,:}

But they both don't work for me. They change the table into a cell, not a double array

Answer 1

[BN]

I believe it's mean that you have non-numeric data in your table.

Try this:

If T is your table, use cell2mat after table2array.

T_cell = table2array(T);
T_array = cell2mat(T_cell); % T_array is output
% if it is single so after this two lines use:
% T_array = double(T_array)

[Abdelrahman Taha]

Well, the table has numeric and text data. I created a new matrix out of the columns in the table that contain numeric data, but i just noticed that the numeric data in this matrix are of char class, not double. Why would that happen?

This is that I've done:

data = readtable('columns.xlsx');
data_num = [data(3:end,3:7) , data(3:end,9:12)];

The data_num is the one to have the numeric data in it.

[BN]

I believe it happens because your first data table includes text and numeric data.

Do you have a problem with using this?

data_numNEW  = table2array(data_num );
data_numNEW  = cell2mat(data_numNEW ); % T_array is output

I do not see your data but if the problem is you have char instead of number this maybe helps you:

data_numNEW  = table2array(data_num );
data_numNEW = cellfun(@double,data_numNEW,'uni',0)

[Abdelrahman Taha]

Thanks so much. That was really helpful.

I've tried both solutions, the first doesn't work, it gives me this error:

Error using cat
Dimensions of arrays being concatenated are not consistent.

However the second worked, but I needed to convert the contents of the cell array from char to string first and then into double. And then used cell2mat to convert the cell array into a matrix

data_numNEW  = table2array(data_num );
data_numNEW = cellfun(@string,data_numNEW,'uni',0);
data_numNEW = cellfun(@double,data_numNEW,'uni',0);
data_numNEW = cell2mat(data_numNEW);

Answer 2

[Chhanda]

My code is this :

data=readtable('MainData.xlsx');
X1= data(:, 3);% Assuming time, temperature, humidity are columns 3, 4, and 5
X2=data(:, 4);
X3=data(:, 5);
% Convert variables to tables
X1Table = table(X1);
X2Table = table(X2);
X3Table = table(X3);
% Extract the dependent variable (soil moisture)
Y = data(:, 6); % Assuming soil moisture is in column 6
n=height(X1);
onesTable = table(ones(n,1));
a = [onesTable, X1Table, X2Table, X3Table];
c=pinv(a)*Y;

I am getting this error:

Error using svd

First input must be single or double.

Error in pinv (line 18)

[U,s,V] = svd(A,'econ','vector');

Error in Project1 (line 21)

c=pinv(a)*Y;

Kindly suggest a solution.I think i need to change my table to double format ..but unable to do so using table2array().

Kindly help.

[Stephen23]

"Kindly suggest a solution."

Use numeric arrays for storing basic numeric data (not lots of superfluous nested tables).

Use curly-brace indexing to access table content:

https://www.mathworks.com/help/matlab/matlab_prog/access-data-in-a-table.html

The PINV documentation clearly states that its input must be SINGLE or DOUBLE (i.e. numeric). Instead of doing that, you are providing it with nested tables.

"Convert variables to tables": they are already tables, why nest them inside more tables? Why do you need so many tables? Lets try it without all of those tables, e.g. by using curly-brace indexing:

T = array2table(rand(7,6)); % fake data alternative to READTABLE
Y = T{:,6};
n = height(T);
a = [ones(n,1), T{:,3:5}];
c = pinv(a)*Y % your approach

c = 4×1

0.5321 -0.1422 0.0876 0.2790

c = lsqminnorm(a,Y) % the recommended approach

c = 4×1

0.5321 -0.1422 0.0876 0.2790