“Northern Lights Over the Cabins,” photo by Frank Wood
Hope all is well and peaceful in your world.
This week’s forums seemed full of map and date questions. So I’ve organized this digest differently. [Let me know what your think.]
One of my favorite topics….
Allan Walker created an impressive set of maps for Utah State University. He used a mix of custom polygons, standard marks, satellite imagery and OpenStreetMap to map police and fire incidents. Be sure to follow the link to his blog where he explains his process. [Nice work Allan!]
Alex Kerin worked out a great way to fill maps by region or state, and toggle between them – all using native Tableau geography, so no need for custom polygons or such. It’s all driven by a simple table calculation and a parameter. Pretty cool huh Cameron?
Ayush Baheti was struggling with mapping marks onto a background image. I’m sure there are lots of different approaches to this, but here’s how I usually work with background images. [If your way is better, please school me.]
Derek Winter posted a question about mapping routes with origin and destination points in one row/record. Both Alex and Richard provided good workable explanations of how to do this, but I suspect each would have included sample workbooks had the underlying data been more readily accessible. [When you post an extract it’s harder to get at the data than if you leave the extract off and expose the Excel file.]
P. Haezel wants to get access to the zoom level variables so he can change his aggregation accordingly. I do too! And so does Richard. [Consider this my ‘Shameless Plug of the Week’, again.]
Other than answering forum questions I rarely manipulate dates, but they can be fun little puzzles….
Brian Comeau’s first ever post asked how to plot holidays so he could tease out any patterns that might be connected to these special dates. The catch: the data was in two different tables. Here’s Alex’s in-depth explanation of how to use multiple tables and multiple custom joins to return ALL the data rows. [I’m not sure how Alex traveled all this past week and managed to answer so many forum questions, but he did, and we’re all wiser for it.]
Alan Eldridge made two important points about working with dates. First, try to avoid strings – he gives examples and tells why. And second, why it’s best to use the ISO date format. [There’s an old movie about this, but I just can’t remember the title. Anyone?]
Donna Trinh’s question about comparing date-time from one row to the next was my date puzzle for the week. Great fun coming up with the solution – take that NYT crossword! [Note: the first stumbling-block for many calculations, and particularly for dates, is the dreaded ‘cannot mix aggregate and non-aggregate values…’ In these cases ATTR() should be the first tool out of your kit.]
Finally… Joshua Milligan used a LAST() function as a filter to help Siddhartha get his workbook to calculate correctly. I used LOOKUP() and a parameter to answer Archana’s question. And Alex showed how to strip the date off a date/time field leaving only time. There were several other date posts, but this section is getting a little long….
Odds & Ends
I came across two very cool vizzes this week.
The first one is a page animation viz by Karan Sehgai. Richard lent a hand getting the reference lines to appear on cue. He used pairs of calculated fields to compare dates and control the lines’ visibility, very slick.
Jason Borucki created the other viz I think deserves a cool-award:
Yeah I know, totally cool; so many possibilities. Make sure you read the tip I gave him for solving his color problem. [And the answer is: Jonathan! He’s the one who taught me this color-picker trick. Thanks again my friend.]
Suzie L. asked a question about nulls and missing values that she and Donna worked through together. Suzie posted a reference to an excellent thread in which Joe, Richard and others explored this issue in depth. Ultimately Donna is the one who “Got it!!” [What is it about Tableau that gets us all so excited when we figure something out?]
Michael Nealey has posted this week’s unanswered question. He’s written a fairly clear explanation of what he’s trying to do and has of course included a packaged workbook. Michael is no newbie; he’s been a member since Feb. 2011 (longer than I have). I’m sure this isn’t a simple problem (though I haven’t had time to work on it). So if you’re looking for a bit of a brain-teaser for this long holiday weekend, why not give this one a go.
The Conversation. [Section deleted.]
Server. I don’t really know what to do about Server questions – I don’t use it or know it. So without guidance I can only guess at what’s important. Here are the discussions that seemed important to me: Run as user – server configuration or Oracle procedures or Mapping & Server [I chose these mostly because Russell took the time to answer.]
As always comments, feedback and criticism are welcome.
Links to Tableau profiles of everyone mentioned in this digest can be found here.