This block implements a function commonly called atan2. Atan2 is version of arctan that takes the (x,y) coordinates of a point and returns the angle from the +x axis to a line that goes from the origin to that point. The angle will be positive for counter-clockwise rotation and negative for clockwise. In degrees, then the output Angle will be in the range -180 to 180; in radians it will be -pi to pi.
Calculators typically give you the arctan function which gives you an angle given by the ratio of the two non-hypotonuse sides of a right triangle. The atan2 function is based on this function but has the added power that it can give you an angle given any (x, y) point as long as x or y is not equal to zero. For example:
Given the point (x,y), this block will calculate the angle labled as θ. Note that the angle will be positive if y is positive and negative if y is negative. The output angle will be in the range of -180 to 180 for degrees and -pi to pi for radians.
This block takes advantage of the floating point math that is available with the LEGO
Mindstorms 2.0 (and beyond) software. The input coordinates can have a fractional component and do not have to be integers. For example, you can pass in a point such as (x = 2, y = 1.5) and the output Angle will be about 36.87 for degrees and 0.64 for radians.
The block’s data hub will open automatically when the block is placed in the work area.
This block can also be used to calculate the standard arctan function if you only provide the value to the y input and leave the x input set to the default value of 1.
You can also use this block to get the constant value for pi. ATan2 of (-1,0), in radians, is pi. To get pi/2, use the coordinates (0, 1).
You can pass data to the ATan2 block dynamically by connecting data wires (from other blocks’ data hubs) to the ATan2 block’s data hub.
Open a block’s data hub by clicking the tab at the lower left edge of the block after it has been placed on the work area.
Data wires carrying input information to a block are connected to the plugs on the left side of its data hub. Data wires carrying output information are connected to the plugs on the right side.
[A] Input plug
[B] Output plug
[C] Number data wire (yellow)
[D] Logic data wire (green)
[E] Text data wire (orange)
[F] Broken data wire (gray)
If an input plug has a corresponding output plug (see A above), the input data will pass through from the input plug to the output plug without being changed. In this case, you can only use the output plug if the input plug is connected to an input data wire; connecting an output data wire to such an output plug without a connected input data wire will cause the output data wire to be “broken” (and colored gray).
Each data wire carries a specific type of data between blocks. For example, if a data wire is dragged from a logic plug on a block’s data hub, it can only be connected to a logic plug on another block’s data hub. The chart below shows what kind of data each plug can accept or send out.
Data wires are identified with specific colors: wires carrying number data are colored yellow, wires carrying logic data are colored green, and wires carrying text data are colored orange.
If you try to connect a data wire to a plug of the wrong data type, the data wire will be broken (and colored gray). You will not be able to download your program if a data wire is broken.
If you click a broken wire you can read why it is broken in the small help window in the lower right corner of the work area.
If an input data wire transmits a value outside the possible range of the plug it is connected to, the block will either ignore the value or change it to a value within its range. For plugs that allow just a few input values (example: just 0, 1, or 2), the plug will ignore the input if a value arrives outside its range.
For plugs that accept larger input ranges (example: 0 – 100), the plug will force any input outside its range to fit. For example, if a Move block’s Power plug receives an input value of 150, the block will change the input value to 100 (i.e., a number within the Power plug’s range).
You must click on the Data Hub to open it as shown.