I'm trying to find a function which does the same thing as the Map() function in Arduino IDE.
I have an int variable that's coming from an ADC. In my arduino code, I use a simple int variable = map(variable, 0, 4095 , 0, 100);
to change the input of that adc to a 0 to 100 but i'd like to do that in Dart.
Is there a simple function for doing this in flutter?
You can simply multiply your new upper range bound by the existing range expressed as a fraction of 1, using the lower range bound as an offset.
variable = ((upper - lower) * (variable / 4095)) + lower;
If you require an integer, you can utilise a rounding or truncation function as well.
I found myself frequently being in need of such a function in my own projects, so I developed the num_remap package.
Using that package, you can remap integers like this:
import 'package:num_remap/num_remap.dart';
...
variable = variable.remapInt(0, 4095, 0, 100);
Related
Is there an easier way of comparing two floats in the metal shading language?
I'm currently multiplying by 1000 then converting to an int to get an integer comparison.
int r = (int)(color.r * 1000);
int checkColorR = (int)(50.0/255.0 * 1000);
if (r == checkColorR) ...
I'm after something like: Mathf.Approximately in Unity
A common technique is to compare the absolute difference to some desired precision:
if (fabs(color.r - 50.0/255.0) < 1.0/1000.0) ...
You can, of course, define a function for this rather than repeating it all over the place.
Your current technique is bad because it does integer truncation. The two values could be very close, but on either side of an integer, and they would compare as not equal because one would be truncated to the integer below. For example, 4.9999 and 5.0001.
Given any number of the sort 78.689 or 1.12 for instance, what I'm looking for is to programmatically round the number to the nearest tenth place after the decimal.
I'm trying to do this in an environment where there is a math.floor() function that rounds to the lowest whole number, and as far as I can tell from documentation there's nothing like PHP's round() function.
There's simple snippet at: http://lua-users.org/wiki/SimpleRound
function round(num, numDecimalPlaces)
local mult = 10^(numDecimalPlaces or 0)
return math.floor(num * mult + 0.5) / mult
end
It will misbehave when numDecimalPlaces is negative, but there's more examples on that page.
You can use coercion to do this...
It work just like printf... You can try to do something like in this snippet.
value = 8.9756354
print(string.format("%2.1f", value))
-- output: 9.0
Considering that this is roblox, it would just be easier to make this a global variable instead of making a single module or creating your own gloo.
_G.round = function(x, factor)
local factor = (factor) and (10 ^ factor) or 0
return math.floor((x + 0.5) * factor) / factor
end
In my case, I was simply trying to make a string representation of this number... however, I imagine this solution could prove useful to others as well.
string.sub(tostring(percent * 100), 1, 4)
so to bring it back to a numerical representation, you could simply call tonumber() on the resulting number.
I am using lua 5.3.2 and the following piece of code gives me an error:
string.format("%d", 1.16 * 100)
whereas the following line works fine
string.format("%d", 1.25 * 100)
This is probably related to this question but the failure depends on the floating point value. Given that, in my case, a local variable (v) holds the float value, and is generated by an expresson that produces a value between 0 and 2 rounded to 2 decimal places.
How can I modify the code to ensure this doesn't fail for any possible value of v ?
You can use math.floor to convert to integer and add +0.5 if you need to round it: math.floor(1.16 * 100 + 0.5). Alternatively, "%.0f" should have the desired effect as well.
Hello well all is in the title. The question apply especially for all those values that can be like NSTimeInterval, CGFloat or any other variable that is a float or a double. Thanks.
EDIT: I'm asking for value assignment not format in a string.
EDIT 2: The question is really does assigning a plain 0 for a float or a double is worst than anything with f a the end.
The basic difference is as :
1.0 or 1. is a double constant
1.0f is a float constant
Without a suffix, a literal with a decimal in it (123.0) will be treated as a double-precision floating-point number. If you assign or pass that to a single-precision variable or parameter, the compiler will (should) issue a warning. Appending f tells the compiler you want the literal to be treated as a single-precision floating-point number.
If you are initializing a variable then it make no sense. compiler does all the cast for you.
float a = 0; //Cast int 0 to float 0.0
float b = 0.0; //Cast 0.0 double to float 0.0 as by default floating point constants are double
float c = 0.0f // Assigning float to float. .0f is same as 0.0f
But if you are using these in an expression then that make a lot of sense.
6/5 becomes 1
6/5.0 becomes 1.2 (double value)
6/5.0f becomes 1.2 (float value)
If you want to dig out if there is any difference to the target CPU running the code or the binary code it executes, you can easily copy one of the command lines compiling the code from XCode to command line, fix missing environment variables and add a -S. By that you would get assembly output, that you can use to compare. If you put all 4 variants in a small example source file, you can compare the resulting assembly code afterwards, even without being fluent in ARM assembly.
From my ARM assembly experience (okay... 6 years ago and GCC) I would bet 1ct on something like XORing a register with itself to flush it's content to 0.
Whether you use 0.0, .0, or 0.0f or even 0f does not make much of a difference. (There are some with respect to double and float) You may even use (float) 0.
But there is a significant difference between 0 and some float notation. Zero will always be some type of integer. And that can force the machine to perform integer operations when you may want float operations instead.
I do not have a good example for zero handy but I've got one for float/int in general, which nealy drove me crazy the other day.
I am used to 8-Bit-RGB colors That is because of my hobby as photographer and because of my recent background as html developer. So I felt it difficult to get used to the cocoa style 0..1 fractions of red, green and yellow. To overcome that I wanted to use the values that I was used to and devide them by 255.
[CGColor colorWithRed: 128/255 green: 128/255 andYellow: 128/255];
That should generate me some nice middle gray. But it did not. All that I tried either made a black or white.
First I thought that this was caused by some undocumented dificiency of the UI text objects with which I was using this colour. It took a while to realize that this constant values forced integer operations wich can only round up or down to 0 and 1.
This expession eventually did what I wanted to achieve:
[CGColor colorWithRed: 128.0/255.0 green: 128.0/255.0 andYellow: 128.0/255.0];
You could achieve the same thing with less .0s attached. But it does not hurt having more of them as needed. 128.0f/(float)255 would do either.
Edit to respond to your "Edit2":
float fvar;
fvar = 0;
vs ...
fvar = .0;
In the end it does not make a difference at all. fvar will contain a float value close to (but not always equal to) 0.0. For compilers in the 60th and 70th I would have guessed that there is a minor performance issue associated with fvar = 0. That is that the compiler creates an int 0 first which will then have to be converted to float before the assignment. Modern compilers of today should optimize automatically much better than older ones. In the end I'd have to look at the machine code output to see whether it does make a difference.
However, with fvar = .0; you are always on the safe site.
I'm implementing line charts of primefaces(3.0) , I'm trying to change the value of X-scale
The values which I'm using are minX="0" maxX="38" , since primefaces linecharts is using jqplot , I added this script
<script>
$(function(){
widget_category.plot.axes.xaxis._tickInterval = 1;
widget_category.plot.axes.xaxis.numberTicks = 38;
});
</script>
But still the coordinates is coming in decimals.
I would like to mention that for Y scale, the values I used are minY="40" maxY="110" with style="height:1005px;" , As i figured out for a scale value , which can be 10 if height is defined as 1005px i.e. 5 * 14 = 70 which means Y scale is of 5 intervals , with 14 values and the line height is 1005 as 5*14*14 = 980 + 25 (which is top-margin added) 1005.
Though the same is not working out for X-Scale.
Any help would be helpful.
The arithmetic in your Y values are all multiplication operations on whole numbers, which will always result in a whole number. These whole numbers correlate perfectly to pixels.
Your X range however involves a multiplication of 1.0 and 38, one being an integer value and the other being determined as a float or double number. When performing a multiplication operation where one number is a float then the result value will always be a float, and standard floating point artithmetic rules will apply. This is why the coordinates are coming in decimals which don't equate perfectly to pixels.
When using Javascript you need to be careful of these kinds of pitfalls because it is not a strongly typed language like Java and it will not point things like this out to you.