Multiplying dataset with numbers

Software and Tools Other - Software and tools
,
1

I would like to multiply a dataset with a real number, e.g.

data = ct.catalogue.retrieve(...)
desired_result = data*3

This gives me the following error message:

774×249 8.27 KB

Is there any way to perform this operation?

Thank you!

2

Dear Georg,

Any additional detail on your workflow would help to understand the  nature of data and why this operation fails.

You could try to use the multiplication operator:

desired_result = ct.operator.mul(data, 3)

Regards.

Vivien


3

Thank you Vivien, your code proposal worked perfectly!

4

Great, glad to know.

I am curious to understand why the * did not work, would you mind sharing the code that was failing?


5

Ok, here's some part of the code:

def power_curve(xar):
'''	
	Simplified power curve of wind turbine
	Cut-in speed 3 m/s
	Nominal power (3450 kw) at 12 m/s
  	Cut-out speed 25 m/s
'''
    xar1 = ct.cube.where(xar > 25, 0, xar)
   	xar1 = ct.cube.where(xar1 <= 25, 3450, xar1)    
   	xar1 = ct.cube.where(xar1 <= 12, 3450/9*(xar1-3), xar1)      # <=== This is the part that fails
   	xar1 = ct.cube.where(xar1 <= 3, 0, xar1)
   	return(xar1)

various decorators…


def application():


data = ct.catalogue.retrieve(
    'reanalysis-era5-single-levels',
    {
        'variable': [
            '100m_u_component_of_wind', '100m_v_component_of_wind'
        ],
        'product_type': 'reanalysis',
        'year': '2019'
        'month': months, # All months
        'day': days,     # All days
        'time': time,    # All hours
        'area': [max_lat, min_lon, min_lat, max_lon] # Some 9 values
    }
)

wind_speed = ct.math.sqrt(data[0]**2 + data[1]**2)
power = power_curve(wind_speed)</pre>
6

Hi Georg, if you do data * 3 instead of 3 * data the * operator actually works.

This is still a bug that need to be fixed but it still allows you to use * and make your code shorter and more readable.

Note that ct.operator has the advantage of handling the units where units are preserved while the +, -, *, / operations always drop the units.

Regards.

Vivien

7

Good to know, thanks!