I know this was a year ago but i had a few beginner questions to help me understand Mathematica. The online help isnt all that helpful.

1. What does "Rest@Import" do exactly? I see that Rest imports without the first item, but I cant find what "@" does and how it relates to Import. There is a reference to @ being a prefix but really hard to understand form the online help what it does.

2. Is "dString, zString" a command in your code? both d and z are lower case so I dont think they are commands but String is uppercase so not sure if that is a Mathematica built-in function and if so, what does this do? Is this a defined variable or function?

3. What does the extra underscore for "z__" do? I thought that a single underscore was a function but not sure in this case what exactly is happening with the second underscore

4. And what does ":>" mean? I searched on it and came up with nothing

5. I know that <> is to join but still trying to understand what that second line is doing step by step.

6. Finally I copied the example and it ran perfectly. But I wasn't able to to a plot using DateListPlot function, I tried and it didnt work. It did work when I took out the second variable and only had a single date with a single variable. So how do I get it to plot when the data is formatted like your example, {{date time }, variable1, variable2}, {date time stamp}, variable 1, variable 2} etc. it didnt seem to recognize that the same date/time stamp applied to two plotting variables (results). I looked and didn't see how to get it to recognize the format. There should be two different lines plotted using the same date/time stamp

Thanks for any thoughts, I know these are beginner questions.

You copied the code incorrectly it is

data = 
  data /. {d_String, t_String, z__} :> {DateList[d <> ":" <> t], z}

rather than

 data = 
 data /. {d_String, t_String, z_} :> {DateList[d <> ":" t], z}

There are two underscores after the z and there is a <> between the ":" and the t.

I executed your suggestion again from scratch with the same result (with the difference that I truncated the data file to make things easier to handle):

 In[1]:= path = "C:\\Users\\User\\Desktop\\ShortTestDataNov2013.csv"

    Out[1]= "C:\\Users\\User\\Desktop\\ShortTestDataNov2013.csv"

    In[2]:= data = Rest@Import[path]

    Out[2]= {{"11/4/2013", "9:05:45", 80.75, 9.4}, {"11/4/2013", 
      "11:06:21", 78.09, 9.4}, {"11/4/2013", "12:40:52", 76.9, 
      9.7}, {"11/4/2013", "15:02:47", 74.27, 9.6}, {"11/4/2013", 
      "15:43:46", 75.16, 10}, {"11/4/2013", "17:24:29", 73.66, 11.4}, {""}}

In[3]:= data = 
 data /. {d_String, t_String, z_} :> {DateList[d <> ":" t], z}

Out[3]= {{"11/4/2013", "9:05:45", 80.75, 9.4}, {"11/4/2013", 
  "11:06:21", 78.09, 9.4}, {"11/4/2013", "12:40:52", 76.9, 
  9.7}, {"11/4/2013", "15:02:47", 74.27, 9.6}, {"11/4/2013", 
  "15:43:46", 75.16, 10}, {"11/4/2013", "17:24:29", 73.66, 
  11.4}, {""}}

I don't see what I'm doing wrong.

Attachments:

Yes that is normal. It is not an error, it is a warning. It is there because the way when interprets a date like 2/3/2014 is ambiguous. In North America it is interpreted one way and in Europe it is interpreted differently. The function DateList can be specified to force one specific interpretation and this is discussed in its documentation. If you look at the output of your running the code, you will see that everything has turned out the way you wanted it to.

You have only executed the first line of the code that I posted. You need to execute both lines. The first line imports the data, and the second line causes the date to be generated in the form that you indicate.

Try this:

data = Rest@Import["/Users/dreiss/Desktop/TestDataNov2013.csv"];

data = data /. {d_String, t_String, z__} :> {DateList[d <> ":" <> t],  z};

The important point in this example is that, indeed, Mathematica does have powerful facilities to handle the date time format that is embedded in your example (i.e., DateList). However, in this particular example the day and time are in separate columns, so you need to let Mathematica know that they need to be combined, otherwise they are distinct data sources.