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Home - General / All posts - Manifold future, some more default fields in tables, e.g., Area
460 post(s)
#21-Sep-17 18:38

Hi, I'm a casual user of GIS in that it may be weeks before I need to use it again. As such I forget syntax. It would be really handy having some default fields, Area being one for areas, maybe length for line objects. Today I need to email someone the hectarage of an area but have forgotten how to generate an area expression in Manifold Future. Instead I'll use M8 turn on intrinsic fields and move the decimal place over 4 to get ha. It would be great if area was a default field in MFuture. I realize different people work in different units but perhaps we can choose a default unit of area in settings or tied to the projection? For me that would be hectares (so I don't have to move the decimal place over from square metres).

There are different categories of users, some who work in GIS every day, all day. Others like me where GIS is a value added service but I can go 6 weeks between firing up GIS and I've since replaced what I learned with something else.


8,090 post(s)
#22-Sep-17 06:32

There are way too many functions that could be potentially useful as computed fields, that's why we don't have any computed fields built-in by default and concentrate on being able to easily add the ones you want.

Adding a computed field for an area seems to be pretty quick: open table window, click the new field header to start adding new field, type the name of the new field, set the type of the new field to some numeric type (eg, float64 - we could perhaps make the list shorter / split it into often-used types and rarely-used types), click 'Set field values', select 'Area' in the list of templates (we could allow filtering by name), make sure the geom field to compute area of is set to the field you want, then change 'Add Field' at the bottom to 'Add Computed Field' and click it.

We can perhaps make it even shorter by adding something like favorites for computed fields and allowing you to right-click the Geom field and select New Computed Field - Area, and then have a set of default favorites. Maybe we should do this.

But in general, try using the Transform dialog for things like that. For simple stuff like computing an area you don't have to write any code, it's all done by clicks. And if there are too many clicks or steps tell us which ones you think are the worst (least intuitive / slowest / unnecessary) and we will try to reorganize the UI, make it more intuitive and faster.

StanNWT80 post(s)
#22-Sep-17 07:20

How about using something similar to how predictive text works, yes I know we all hate it I our smartphones, however, if a predictive list of field types or calculations you would want to do could be selected by typing in a pop up box when you cluck add field the choose the name.

When you choose the kind of field type another box that allows you to type and a list if transforms / calculations / automatically starts zeroing in on what the options are the more you type from the existing lust of possible keep ones in Radian.

Not that this is easy to do or would be wanted but might solve an easy contextual way of allowing people to get perimeter, area in km2 or m2 or acres or hectares or anything else regardless of whether we're talking about a geometry field or not.

The way to think it is the way google's predictive search works as well as the way python I think predicts what you're trying to do as you type the code. I'm not a programmer so forgive the python reference. I've been doing GIS since DOS but hate writing code.


8,090 post(s)
#22-Sep-17 08:14

Yes, sure, we do filtering similar to what you describe in many places already where what you type restricts the range of possible choices. We might also do autocomplete when entering an expression (or query). We agree this is helpful, it is on the wishlist.

460 post(s)
#22-Sep-17 18:51

Yes, something like predictive text with pop-up explanations and syntax examples much like in MS-Excel, as you start typing a formula (e.g., =count... then all the count variations and expression forms appear). In anycase, some kind of expression builder with help. M8 had predictive text when building functions, the possible field names or function names would appear.

I attach two screen shots, first is in Manifold Future where I add a field, set to a real number, and do a search for "area" hoping I'd find the likely function or query. But I get an error. I did this once before months ago and I think I have to replace some of the text in quotation marks with something particular to the table, but I don't remember exactly what. Some popup help would be useful. I know I should RTM, but this is a quick query, I just need to send an email and tell someone the area. The email is the task, not the GIS task.

Second screenshot is from QGIS, I click away at the choices that appear and build my expression. There is some help text. I got it first try to show square metres. It's an easy next step to divide by 10,000 to get hectares. I see a preview of the calculation, 8411454.4 ha. Done. Sent my email, back to work.

The expression builder in Manifold Future and R9 is a huge step forward compared to M8 which I never used to full potential using queries or functions. Building on MF, help text and example expressions would be really helpful. Also if the dialog window could show a preview of the intermediate result of the expression as it is being built would be helpful as confirmation the expression is being constructed correctly.

Another idea, in building expressions in MF, some arguments are optional, what if when the user does not change the default value for an argument text, say "tolerance" that either the optional argument falls away or is set to some default value? This happens in MS-Excel, for instance when calculating PMT (interest payments, the default is interest charged at the beginning of the period, by entering a "1", interest is charged at the end of the period (I don't remember exactly but it's explained in the popup help text). If I don't specify when interest is charged, it defaults to the beginning of the period which is the most common situation.

Area expression QGIS.JPG
Area expression.JPG

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