Sort Descend Scientific Notation Error

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Kiran Eswaran
Kiran Eswaran on 14 Oct 2019
Commented: Stephen23 on 15 Oct 2019
I've got a vector of numbers. The vector has some numbers stored with and without scientific notation.
Eg 0.01 and 9.8e-04.
When i try sorting these numbers in descending order, the sort function puts 9.8e-05 above 0.01, even though 0.01 is larger.
Can anyone help me so it sorts from largest to smallest based on the expanded values? I've been trying to convert the numbers in the matrix from scientific notation to standard form, but changing format has not helped, and i haven't been able to get rid of the scientific notation properly.
I've looked through past questions / answers and have not found an answer that has worked for me.
Any advice is appreciated.
I believe the issue may be that the numbers are considered strings, but unsure how to convert string scientific notation to numbers.
Example data and code:
u =
[ APH 0.01
GPT 9.8e-04
CPH 6.4e-05]
[~,idx] = sort(u(:,2),'descend');
sortedu = u(idx,:);
sortedu looks like:
sortedu =
[GPT 9.8e-04
CPH 6.4e-05
APH 0.01]
edit: updated code.
Kiran Eswaran
Kiran Eswaran on 14 Oct 2019
Edited: Kiran Eswaran on 14 Oct 2019
Adding on to that point, the initial stock data were stored in a cell. I extracted from the cell as a string (string(cellname)), and then converted the string using str2double, as str2num didn't work for me.
  • str2double(string(cellname));
I guess a better way to frame my question:
How can i change the string scientific notation (eg 9.8e-04) to a number.
Stephen23 on 15 Oct 2019
@Kiran Eswaran : please upload your original data in a .mat file, by clicking the paperclip button. Note that I wrote "original data": this means your original table u (or whatever it is called), before you tried to do any conversions.

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Answers (1)

Jos (10584)
Jos (10584) on 14 Oct 2019
Edited: Jos (10584) on 14 Oct 2019
You misuse the sort command. Simply:
sortedu = sort(u ,'descend')
would do :-)
Moreover, if you remove the semicolons, you would see that you have some strange results in between...
Ask yourself what u(:,2) does, and u(idx,:).
  1 Comment
Kiran Eswaran
Kiran Eswaran on 14 Oct 2019
Apologies, i framed the initial code incorrectly and have updated it.
I think the issue is that the numbers are stored as strings in scientific notation form (eg 9.8e-04) and so i'm unsure how to convert this string scientific notation to a number. I believe solving that conversion will solve the sort issue.

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