Why not just take the solution provided by pdsolve and substitute x= exp(t)? As in

Sol:= pdsolve({sys});
subs(x= exp(t), Sol);

@tomleslie 

Yes, that's another tacit list conversion, and it works fine. However, I want to encourage the OP to avoid making tables in the first place---I doubt that they have any explicit use for a table. This OP in particular has a habit of assigning to sequential indexed entries. Users eventually need to learn that that doesn't create a list or even an array.

@tomleslie 

Certainly this isn't the intended behavior. I believe that it's a failure of the MaplePrimes editor's equation editor.  But a new user can't be expected to know that that editor doesn't work. Even when it does work, the output isn't very good looking:

The letters are wavy, not crisp. Some parentheses should be added to reduce ambiguity.

Yes, I agree that the use of this should be discouraged.

@acer I've had this problem also. I'll try to recall the details: It was in Windows and in a Document Block. All output, no matter how lengthy, was deferred until the end of command execution. This includes the output of print statements, userinfo statements, and using option trace on procedures. I just assumed that it was one of the numerous hideous features of document mode rather than a bug.

@tomleslie 

I believe (I'm not sure) that when an image appears in a post as a blue square with cut corners and a black capital italic A, that it isn't the user's fault; rather, it's a failure of the MaplePrimes editor's equation editor. Using Firefox (but not Chrome), I can right click on the square and select the option View Image Info. In the box that pops up, one of the fields is Associated Text. The contents of that field are

sum(xj*(sum(yi, i = k .. n)), j = k .. n)

which I liberally interpretted as being intended to be

sum(x[j]*(sum(y[i], i = k .. n)), j = k .. n)

If I've read this correctly, the code beneath your image is

sum(x[j]*sum(y[i], i= k..n), j= k..n).

You ask for help to "solve" this. What does "solve" mean in this context? One usually solves equations or inequalities; the above is simply an expression. Do you mean simplify it, or find a closed form? That can't be done: The expression is too general.

Please upload the data file data1.csv.

@rolfjg I see now that you're working with a fairly old Maple (Maple 12). From the error message that you showed, I suspect that the datasetlabels option was added after Maple 12. I had no way of knowing that since the version where features are added is only very inconsistently mentioned in the help files.

I always would much rather have an actual command than something "interactive". So, try this (with both x and y being lists):

Statistics:-ColumnGraph(zip(`=`, x, y));

I'm 95% sure that this will work in Maple 12. If not, let me know, and I'll come up with something else.

@Markiyan Hirnyk This page implies that there's a MapleSim 7:  http://www.maplesoft.com/support/downloads/maplesim/msim7_01update.aspx

@tomleslie It's in the DTM worksheet. Look for it as the Greek letter, not spelled out.

I recommend that you never use the initialcondition command.

I've been using Maple for 16 years and answering questions about it online for nearly that long. I've answered many thousands of questions, and I've read the answers to many thousands more. Surely a few thousand of those questions have been about ODE systems. Yet in all that time I've never seen the initialcondition command. But, sure enough, I checked the help, and it exists. Clearly this command is not used in practice. And upon reading its minimal help file, I can see no practical use for it. Does anyone know what it's for? Is it part of some project/package that was never finished?

Your b[1], ..., b[4] are not differential equations: they contain no derivatives.

Yes, please upload your worksheet.

@acer I agree totally. Indeed, I almost added "However, I agree with Acer that that's not a good reason to avoid restart," but I didn't want to put words in your mouth.

Still, there may be other more-valid reasons to unassign all variables (or all variables of a certain type), and the above command is not-at-all obvious: Angle brackets are the only brackets that work.

@tomleslie Maple doesn't seem to have a problem plotting (in 2-D) things that get infinitely steep if you include the coordinateview option (or view option). For 3-D plots, it's a different story.