I took the original post to mean drawing a graph of the equation. If this is the case then what you have to do is take what ever the equation is and then calculate values of y based on chosen values of x, this is what 1beginner1 code is essentially doing but for a single value of x.
So for your eqation: y = 4x^2 + 2x^3 + 12 you would step through values of x and calculate values for y.
There are different ways of drawing the graph, the method I use is to calculate points along the graph and then join the points with straight lines. If you increment the values of x in suitably small amounts the curve will appear smooth as the distance between points will be short. You could use dots but I find this more of a hassle as you end up having to fill in the gaps between the dots.
An example of how to do all this:
`This program generates a graph of an equation be calculating points along the graph
`and joining those points using straight lines
hide mouse
`The for to next loop set the range of x values you want to use and the "step" value gives
`the increments you want to use to draw the curve.
point_number = 0
for x = 45 to 360 step 1
inc point_number
if point_number = 1
`this is essentially the first point so we note the value but we need a second point to draw a line
new_x# = x
new_y# = _y_equals_function_of_x(new_x#)
else
`this deals with the all the points after the first
`save the last point
old_x# = new_x#
old_y# = new_y#
`calculate the next point on the graph
new_x# = x
new_y# = _y_equals_function_of_x(new_x#)
`draw a line between the old point and the point just calculated
line old_x#,old_y#, new_x#, new_y#
endif
next x
wait key
end
function _y_equals_function_of_x(x#)
`this function hold the equation that you want to draw out, in this case a sine wave
`this equation can be anything you want it to be
y# = 100*sin(x#)+200
`the reason for putting the equation into a function is because it is called in two different points
`in the main for to next loop
`there might be a better way of generation
endfunction y#
I've used a sine wave as it's a little more fun than a quadratic but you can swap the equation for anything you want.
There are a couple of things to look out for. First, in 2d the origin is at the top left of the screen and postive y is downward. This has an effect of flipping the graph over (like a reflection of a mountain viewed on the surface of a flat lake on a cold crisp morning with nothing to do but... sorry, getting side tracked
). The second thing to look out for is the scale of the x axis, if you swap the sine equation for your quadratic, then what happens is you get a very steep curve that "hugs" the left hand side of the screen. To stretch the curve out a bit you will need to scale the x coordinate by a suitable multiplication factor but this multiplication factor can not interfere with the equation when calculating values of y, it has a purely visual role. The third is the position the zero coordinate if you want to show draw the x and y axis to the screen. Essentially the "+100" in the equation I used moves the entire graph down the screen by 100 pixels. So if you wanted to have an equation "y# = sin(x#)" then half the graph will be off the top of the screen (off the top of the screen are negative values of y). Also, if you want the x axis to start, say, ten pixels from the left edge of the screen then you would have to add this offset to the x coordinate for drawing purposes. Again this offset can not be allowed to interfere with the equation itself but is purely to sort out the visuals. In other words, what you might have to do is split the values you are calculating from the values that you use to plot the graph to the screen.
Ok, that's a big chuck of writing that probably doesn't make sense. So I suggest that you play with the code, try out some different equations and see what you can make of it. If this is what you were asking for in the first place.
