LoadingData - Revision history

Rb at 14:02, 10 November 2014

2014-11-10T14:02:42Z

Rb at 13:52, 10 November 2014

2014-11-10T13:52:35Z

Rb at 13:50, 10 November 2014

2014-11-10T13:50:23Z

Rb: /* CSV files */

2013-10-10T13:32:12Z

‎CSV files

Rb: /* MATLAB R2011 and lower */

2013-10-08T12:25:53Z

‎MATLAB R2011 and lower

Admin: /* MATLAB R2011 and lower */

2012-10-11T13:18:17Z

‎MATLAB R2011 and lower

130.88.57.243: /* CSV files */

2012-09-28T13:46:02Z

‎CSV files

130.88.57.243: /* CSV files */

2012-09-28T13:45:51Z

‎CSV files

130.88.57.243 at 07:57, 25 September 2012

2012-09-25T07:57:43Z

Admin: /* CSV files */

2012-09-24T12:29:10Z

‎CSV files

← Older revision		Revision as of 14:02, 10 November 2014
Line 40:		Line 40:

	Often MATLAB will get the dates right, but there are situations where MATLAB does not get the date-info correctly. One reason for this can be that the MATLAB and Excel are using different reference days. As mentioned above, day 1 in MATLAB is 1 Jan 0000, whereas day one in Excel is 1 Jan 1900. It is prudent to check that MATLAB has done the right thing.		Often MATLAB will get the dates right, but there are situations where MATLAB does not get the date-info correctly. One reason for this can be that the MATLAB and Excel are using different reference days. As mentioned above, day 1 in MATLAB is 1 Jan 0000, whereas day one in Excel is 1 Jan 1900. It is prudent to check that MATLAB has done the right thing.
		+
		+	Here is some guidance on how to do that. Let's say you are importing a dataset where you know that the first observation is for 22 Sept 2012. Once the data are in MATLAB check what the value for the first date is. If it is still in text format, i.e. "22/9/2012", then you know that you are yet to translate it into a MATLAB date format. However, if you encounter the number 735134, then you know that MATLAB has already translated the date into its own format. Whether it has done so correctly you can check using
		+
		+	<source>>> datevec(735134)
		+	ans =
		+	2012 9 22 0 0 0
		+	</source>
		+
		+	which returns the correct date (in the "YYYY MM DD hh mm ss" format). If however MATLAB has the number 41174 as an entry, then the translation did not take the different reference date into account. The number is the Excel date number (as 22 Sept 2012 is the 41174th day when starting with 1 Jan 1900).
		+
		+	How can you correct this? Fortunately the correction is pretty easy. Lets assume that your dates are in a vector called <source enclose=none>dateold</source>, then you can re-base the date vector as follows:
		+
		+	<source> datenew = dateold + (735134-41174) # rebasing date vector
		+	</source>
		+
		+	When you do that, it is vital that you add a comment to the code to remember why you did that. Otherwise it will the reason for a lot of head-scratching if you open the code a few months later.

	== CSV files ==		== CSV files ==

@@ Line 39: / Line 39: @@
 Importing EXCEL data works in the same way as for earlier versions if you use the command line. The difference occurs if you import data by double clicking on the file. Now MATLAB will automatically recognise if any of the input data are dates and if it finds any suggest that these are imported as <source enclose=none>datenum</source> type data.
-Often MATLAB will get the dates right, but there are situations where MATLAB does not get the dateinfo correctly. One reason for this can be that the MATLAB and Excel are using different reference days
+Often MATLAB will get the dates right, but there are situations where MATLAB does not get the date-info correctly. One reason for this can be that the MATLAB and Excel are using different reference days. As mentioned above, day 1 in MATLAB is 1 Jan 0000, whereas day one in Excel is 1 Jan 1900. It is prudent to check that MATLAB has done the right thing.
 == CSV files ==

← Older revision		Revision as of 13:50, 10 November 2014
Line 38:		Line 38:

	Importing EXCEL data works in the same way as for earlier versions if you use the command line. The difference occurs if you import data by double clicking on the file. Now MATLAB will automatically recognise if any of the input data are dates and if it finds any suggest that these are imported as <source enclose=none>datenum</source> type data.		Importing EXCEL data works in the same way as for earlier versions if you use the command line. The difference occurs if you import data by double clicking on the file. Now MATLAB will automatically recognise if any of the input data are dates and if it finds any suggest that these are imported as <source enclose=none>datenum</source> type data.
		+
		+	Often MATLAB will get the dates right, but there are situations where MATLAB does not get the dateinfo correctly. One reason for this can be that the MATLAB and Excel are using different reference days

	== CSV files ==		== CSV files ==

@@ Line 50: / Line 50: @@
 where the first '1' indicates that MATLAB should ignore one row at the top of the sheet and the second '1' instructs MATLAB to ignore one column at the left of the sheet. Also consult <source enclose=none>doc csvread</source> for more details on this import function.
 However, if you need the date information it is easier to first save the file as an Excel file and then import into MATLAB.
 = Dealing with Date vectors =

@@ Line 29: / Line 29: @@
      [NUM,TXT,RAW] = xlsread('MSFT.xlsx')
-which will save the content of the EXCEL file ([[media:MSFT.xlsx]]) into three files. The complete spreadsheet is saved in <source enclose=none>RAW</source>, all numerical entries are in <source enclose=none>NUM</source> and all text entries are in <source enclose=none>TXT</source>. This command works if the data you want to import are on the first sheet in the EXCEL file. If you have several shhets in your EXCEL file and you want to import the data of a particular sheet you can achieve this by means of:
+which will save the content of the EXCEL file ([[media:MSFT.xlsx]]) into three variables. The complete spreadsheet is saved in <source enclose=none>RAW</source>, all numerical entries are in <source enclose=none>NUM</source> and all text entries are in <source enclose=none>TXT</source>. This command works if the data you want to import are on the first sheet in the EXCEL file. If you have several shhets in your EXCEL file and you want to import the data of a particular sheet you can achieve this by means of:
      [NUM,TXT,RAW] = xlsread('MSFT.xlsx','MSFT')

← Older revision		Revision as of 13:45, 28 September 2012
Line 50:		Line 50:

	where the first '1' indicates that MATLAB should ignore one row at the top of the sheet and the second '1' instructs MATLAB to ignore one column at the left of the sheet. Also consult <source enclose=none>doc csvread</source> for more details on this import function.		where the first '1' indicates that MATLAB should ignore one row at the top of the sheet and the second '1' instructs MATLAB to ignore one column at the left of the sheet. Also consult <source enclose=none>doc csvread</source> for more details on this import function.
		+	However, if you need the date information it is easier yto first save the file as an Excel file and then import into MATLAB.

	= Dealing with Date vectors =		= Dealing with Date vectors =

← Older revision		Revision as of 07:57, 25 September 2012
Line 89:		Line 89:

	The answer 4 indicates that this particular genius was born on a Wednesday (1 = Sunday, 2 = Monday, etc.).		The answer 4 indicates that this particular genius was born on a Wednesday (1 = Sunday, 2 = Monday, etc.).
		+
		+	= Example Video =
		+
		+	This video clip demonstrates the import of data from an Excel file and some of the basic date formatting. [http://youtu.be/jyb68zGM2ik ExampleClip]

@@ Line 45: / Line 45: @@
      DATA = csvread('MSFT.csv')
-If you execute this line with this LINK TO THIS FILE!!!! 'MSFT.csv' file you will actually get an error message. This file contains the date information in the first column and the <source enclose=none>csvread</source> function does not really know how to handle these. To avoid this, you can tell MATLAB to only import a certain section of the spreadsheet. For instance, if you want it to not import the first row and first column (which in this particvular case contains the non-numeric information) you can use
+If you execute this line with this LINK TO THIS FILE!!!! 'MSFT.csv' file you will actually get an error message. This file contains the date information in the first column and the <source enclose=none>csvread</source> function does not really know how to handle these. To avoid this, you can tell MATLAB to only import a certain section of the spreadsheet. For instance, if you want it to not import the first row and first column (which in this partivular case contains the non-numeric information) you can use
      DATA = csvread('MSFT.csv',1,1)