I'm working on a survey using the build tool, and I'm would like to

calculate a percentage based on previous responses

Specifically

Q1. Average live weight

Q2. Average carcass weight

Q3. Dressed percentage

For question 3, I want to display the calculation of CarcassWt/LiveWt as a

percentage, and use the acknowledge button to accept (or swipe back and

edit earlier responses)

in the binding section for Q3, I'm using

```
type="decimal" calculate="(/data/CarcasWt) div
```

(/data/LiveWt) * (100)"/>

But I'm getting results like 0.87736256333862

I know it needs some sort of constraint language, but what will give me a

percentage with only 2 decimal places? I don't even care rounded up or

down.....

Thanks all.!

Ruth

There is a round(field, power-of-ten) function. For integer percentages,

you would use:

`type="decimal" calculate="round( (/data/CarcasWt) div (/data/LiveWt) * (100) , 0)"/>`

https://opendatakit.org/help/form-design/binding/ (similar to Excel).

Unfortunately, while the round() is handled with precision in the numeric

value, for some of these values, when they are displayed as a string, they

end up having a chain of zeros followed by non-zero values (e.g.,

1.330000021).

This is because some values are not representable in a binary number system

(e.g., 1/3), and because there is an inconsistency somewhere in the forms

processor when it converts these values into strings for display.

## ยทยทยท

On Wed, Apr 27, 2016 at 12:22 PM, Ruth Little wrote:
I'm working on a survey using the build tool, and I'm would like to

calculate a percentage based on previous responses

Specifically

Q1. Average live weight

Q2. Average carcass weight

Q3. Dressed percentage

For question 3, I want to display the calculation of CarcassWt/LiveWt as a

percentage, and use the acknowledge button to accept (or swipe back and

edit earlier responses)

in the binding section for Q3, I'm using

```
type="decimal" calculate="(/data/CarcasWt) div
```

(/data/LiveWt) * (100)"/>

But I'm getting results like 0.87736256333862

I know it needs some sort of constraint language, but what will give me a

percentage with only 2 decimal places? I don't even care rounded up or

down.....

Thanks all.!

Ruth

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--

Mitch Sundt

Software Engineer

University of Washington

mitchellsundt@gmail.com

Hi? I worked around percentage formatting by performing the calculation e.g

${Q1} div ${Q2} * 100, Then i referenced the calculation like this,

${percentage_calculation}%.

It serves the purpose now.

## ยทยทยท

On 27 Apr 2016 22:22, "Ruth Little" wrote:
I'm working on a survey using the build tool, and I'm would like to

calculate a percentage based on previous responses

Specifically

Q1. Average live weight

Q2. Average carcass weight

Q3. Dressed percentage

For question 3, I want to display the calculation of CarcassWt/LiveWt as a

percentage, and use the acknowledge button to accept (or swipe back and

edit earlier responses)

in the binding section for Q3, I'm using

```
type="decimal" calculate="(/data/CarcasWt) div
```

(/data/LiveWt) * (100)"/>

But I'm getting results like 0.87736256333862

I know it needs some sort of constraint language, but what will give me a

percentage with only 2 decimal places? I don't even care rounded up or

down.....

Thanks all.!

Ruth

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1 Like

Hi

Would you give me an example for this percentage calculation in an excel sheet.

This should be the correct answer, and I'm a bit unclear why you added the caveat. `round(1 div 3 * 100,0)`

will give you "33" [no decimal places], `round(1 div 3 * 100,1)`

will give you "33.3" [1 decimal place], etc. Could you give an example where this will produce an unexpected result?

2 Likes