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why does matlab seperate my column of identifiers and row of column headers from the data? what function puts them back together?i have created a new column of data that needs to be put together with the original data, how do i attach that?

Asked by john borsellino on 14 May 2013

what function will recombine my dataset when matlab automatically seperates my id column and row headers from the data

2 Comments

Walter Roberson on 14 May 2013

How are you reading the data in? Are your headers text strings? Is your data numeric ? When you say you need to put them back together, then are you wanting to produce a text array or a numeric array?

john borsellino on 15 May 2013

i can import the data from an excel file or a tab delimited file, matlab seperates the identifier column(made up of characters..ex. 1456710_at) and the row of column headers(made up of characters...ex. mrl control 1) from the data(made up of numbers only)..i get 1 variable, "data" and a 2nd variable "text data" both are different sizes...i have created a new column from the "data" and i want to put the "text data" and the "data" and the new column of data together and export into excel...so "what function will recombine my 'data' and 'text data' variables with my new column...thankyou for your time and input...i think we want to call it a "dataset" in matlab jargon

john borsellino

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2 Answers

Answer by Walter Roberson on 16 May 2013
Accepted answer

Use the three-output version of xlsread(), and use the third output, "raw". It will reflect what is in the original file.

The first output, the numeric data matrix, will automatically have initial text rows removed (under the assumption that they are column headers) and will also have initial text columns removed. I think it also has trailing rows and columns that are entirely NaN removed. This is because one of the most common operations on an excel file is to work just on the numeric portion, as a numeric array. Numeric arrays cannot have strings in them.

The third output, "raw", will be a cell array, not a numeric array. And that does mean that if you want to extract the numeric subset of it, you are going to have to convert that subset to a numeric array (cell2mat()) if that is the form you want to operate on.

When you go to write out the data, you will be needing a cell array, if you want to have both numeric values and strings.

2 Comments

Image Analyst on 16 May 2013

Rereading your question, I think Walter is right - you want the third output: the "raw" cell array. If you use the first two only, they are not aligned since each one starts with the upper left (1,1) at whatever cell in Excel that type of data started. For example your text cells may start at cell A1 ((1,1) of the test cell array = cell A1 of the Excel worksheet), while your numbers cell (1,1) will be cell A2, not A1 (if your numbers start under a row of text column headers).

john borsellino on 16 May 2013

thankyou guys, i will study up on "cell arrays", thanks for explaining matlab a little bit for me..i have my work cut out for me..(groan)

Walter Roberson
Answer by Image Analyst on 15 May 2013

Does it look all separated when you open it up in Excel? If so, then you wrote out the workbook using strings in xlswrite() instead of cells. If the string is inside a cell, then the whole string will be in one Excel cell. If you just used xlswrite to write out strings, then it will put each character into its own cell in Excel. So tell me (1) did you write out the workbook with xlswrite(), and if so, (2) do you have one character per Excel cell?

4 Comments

john borsellino on 15 May 2013

can you recommend a good study book for matlab?? the manuals i downloaded from the official site are kinda garbage...they do NOT explain things well at all...thanks for your time and input

john borsellino on 16 May 2013

sorry, but i cannot let the data into a public forum...thanks for the excel link info, though. i need to make sure my 'excel link' is working properly, and i will study on those functions, thanks for your time and input

Image Analyst

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