Fix for " The input to DATENUM was not an array of strings."

I am attempting to use datenum on my table (one column, first column) of dates to convert it into a separate variable of just a series of numbers

dataset = readtable('equity_dataset_30.csv');
data = dataset(:,2:31);
date = dataset(:,1);
date_num = datenum(date, 'yyyy-mm-dd');

This last line keeps returning the error: " The input to DATENUM was not an array of strings."

Could someone show what I'm missing here?

Answer 1

[Steven Lord]

The variable dataset is a table. When you index into a table with parentheses, the result is also a table. When you index into a table using curly braces, the result is the type of the underlying data. Compare:

x = (1:5).';
y = int8(x.^2);
T = table(x, y);
tableSubarray = T(1:3, 'x');
doubleSubarray = T{1:3, 'x'};
int8Subarray = T{4:5, 'y'};
whos tableSubarray doubleSubarray int8Subarray

You don't want to pass something like tableSubarray into datenum -- you want to pass something like doubleSubarray or int8Subarray (only you want to specify a char array, not a numeric array.)

Once you have the subarray of your table containing character representations of your dates, I recommend that you convert them into a datetime array rather than converting them into serial date numbers using datenum.

[Ming Au]

Thank you very much this solved my question!

[Peter Perkins]

Steve's right, but perhaps even simpler, if you want to access a single variable, would be

doubleSubarray = T.x(1:3);
int8Subarray = T.y(4:5);

Answer 2

[Massimo Zanetti]

Most probably your variable "date" is not an array of strings.

[Ming Au]

Thanks I thought this might be the problem so I tried converting my date column into an array of strings using

num2str(date)

but it returns the error message: "You can not subscript a table using only one subscript. Table subscripting requires both row and variable subscripts."

-My date column is currently formatted like this...

'2005-01-03'

'2005-01-04'

'2005-01-05' ...and so on.

How should I go about converting my date column into an array of strings so I can use 'datenum' on it?

[NN]

kindly see the below code .i also get the same error.kindly advice

%reading date 
Data=readtable('2019_SysLoad.xlsx');
save 2019_SysLoad.mat Data
testdates=Data((5834:end),1)};

testdates1=datenum(testdates1,'mm-dd-yyyy');

[Walter Roberson]

testdates = Data{5834:end,1)};

[NN]

thank you .But it gives the following error

Invalid expression. When calling a function or indexing a variable, use parentheses. Otherwise, check for

mismatched delimiters.

[Walter Roberson]

testdates = Data{5834:end,1};

[NN]

thank you .It worked.

But i am getting spike like output when i plot datenum and forecasted output.Doesnt look lik wave form .

Kindly advice

[Walter Roberson]

I do not see any obvious problem with the plot. It looks to me like what you would expect for a plot displayed with an unfortunate aspect ratio. Try zooming it.