Subject: Expression builder Posted: 4/22/2015 Viewed: 16360 times
what is the use of expression builder for annual activity level for any agricultural demand site
Ms. Stephanie Galaitsi
Subject: Re: Expression builder Posted: 4/23/2015 Viewed: 16353 times
The Expression Builder allows you to use functions to build expressions (Functions tab) or call in data/results from other branches of the data tree (Branches tab). Overall, the Expression Builder allows you more options when entering data.
An example of a function would be a growth function that specifies how the agricultural area is expanding over time.
For calling in data from elsewhere in WEAP, an example would be that the agriculture annual activity level (probably area) has a relationship to the number of people in the nearby demand site. You'd use the Branches tab, drag the name of the demand site down, and then in the pop-up menu choose Annual Activity Level (probably people, or [cap]). In the white window, you can use this variable to specify the relationship, for example 20*[Annual Activity Level[cap]] (it will populate with the name of the demand site). That says for every person, there will be 20 units (such as hectares) of agriculture.
There is a section in the WEAP tutorial about Using the Expression Builder: it's in the module "Basic Tools."
Ms. Mitika Farkya
Subject: Re: Expression builder Posted: 5/1/2015 Viewed: 16259 times
can you explain how to import data for a river and how much period's data can be entered for any river.
what should be the current accounts year if I have headflow data from 1978.
Ms. Stephanie Galaitsi
Subject: Re: Expression builder Posted: 5/5/2015 Viewed: 16249 times
I like my Current Accounts year to overlap with a full year of data, so you can start in 1978 or 1979 (or specify to have your model start in 1978 with your first full month of data - many options!). And there's nothing stopping you from starting later as well - just make sure you have enough years of data to calibrate your model - try to include time periods with drought or flooding so you can see how your model handles extremes.
To import data from a river, you need a CSV document with the first column for years, the second for months, and the third for measurements (the data). It can also have text above that - WEAP won't read any lines starting with text.
When importing, you want to start by inputing flow data for as far upstream as possible (ideally the headwaters). Clicking on the name of the river in the data tree will bring you to the headflow. Then (making sure you're in the Current Accunts year), click the white box where the data is entered, and a small arrow will appear on the right. Click that and select "ReadFromFile Wizard". Then find your CSV document. WEAP will automatically populate the model with the years in the CSV file.
One word of warning - make sure the units in the CSV file match the units in the river headflow. Save you some trouble later on!