My TA noticed that plots in Excel files do not always show up properly on the Teacher app. There were several times when the plot looks blank, or maybe has 1 or 2 point on it, but if we download their file from the browser and open it in Excel on the computer, we see the real plot with all the points and a trend line, etc.
I confirmed this is the case, and I also compared it to the view on the browser in Speed Grader, and it looks the same to me. That is, if the plot shows up blank in the Teacher app, it also does so on the browser on a PC. Thus, this is not specific to the app, but a general deficiency in the way that Canvas displays Excel files in grading mode. It is too bad, as this severely degrades the usefulness of the app for grading.
After posting I explored some more and I discovered that even in cases where I could see the plots, they did not match the plots in the downloaded file (at all). Its as if Canvas's Excel file interpreter just chose to plot the data in the way it wanted to, not how the student actually did it. In a way, this is far worse. At least, if there is no plot, I know something is wrong. If I see a plot, but it looks wrong, I am likely to count the student off.
Bottom Line: We cannot trust what we see in Canvas SpeedGrader (mobile or browser) when it displays Excel files, at least in terms of plots. (However, I cannot guarantee that it is limited to just plots. This may be a sign of something more fundamentally wrong.)
@kevin_redding , if not already done, I suggest having your TA submit a "Report a Problem" if available on your campus, ideally from a SpeedGrader page where the Excel rendering issue appears. Canvas recently replaced a vendor's failing preview/annotation platform with one of their own design; this new subsystem continues to receive improvements.
(Excel previews were also faulty in the old preview platform, for what that's worth.)
Given the complexity of an Excel spreadsheet document containing graphs/plots, I would suggest that any teaching team download and review the original submission file before giving a grade.
Well, of course, now that I know that, we're downloading the files, because we cannot trust the view in Canvas.
I just wanted to give a warning to people. It is one thing if a function is obviously not working. At least you are aware of it. It is far worse when a function looks like it is working properly, but is actually defective. That could cause people to waste a lot of time.
In my opinion, Canvas should not even try to show Excel files in their preview view. If you cannot do it right, then don't do it at all. Anything in between is potentially dangerous. (Or at least have a floating warning like "plots may not appear correctly in this view" or something like that. We saw no warning at all.)
By the way, I did not see a possibility to "Report a Problem" in the SpeedGrader. Maybe our version does not have that.
I'm sorry to hear that you and your students were affected by this inaccuracy in how doc viewer is apparently displaying plots in Excel preview. Submitting a report to Support is the best way to be kept informed as updates are available on a fix for this issue. In my own personal experience I concur with Rob said about displaying more complicated spreadsheets in previewers being difficult in general.
There seems to be more than one way of doing that. (Frankly, support seems overly complicated in Canvas...)
Do you have a specific link I should use?
Thanks for following up. For anyone else reading along, your instance of Canvas may not look the same as Kevin's based on what customization choices your local admins have made but for Kevin, he should go to the Help option in the global nav on the left side when logged into Canvas and then choose Report a Problem. ACUE will decide whether to escalate your bug report to Instructure's Support team or respond locally in another way.
Thank you for taking a look at this issue. I recently opened a support case for this and received a reply that said this was intended functionality. Have you heard similar feedback?
You received a response from support that Excel files are displayed inaccurately in SpeedGrader by design? If that is the case please email or DM me the ticket number.