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I've got this program I'm working on it's nothing big it has 2 command buttons sin and one cosin what is supposed to happen is when a user enters a number in a text box and depending on which button they click the program will draw lines example if the user enters an 8 and clicks the sin button 8 jagged looking lines will be drawn the larger the number entered the smoother looking the line can anyone help with this? If it will help any I can post what I already have.
Not sure about what you are trying to do, and do you want explanation on how to draw such a geometric line or you want to know something else ? Actually it is really hard for people here to know what you got stuck with ? I mean it is not about the code snipet you will post up here but about what you aren't able to go on with what you have done so far...Quote:
Originally posted by JerryShane
I've got this program I'm working on it's nothing big it has 2 command buttons sin and one cosin what is supposed to happen is when a user enters a number in a text box and depending on which button they click the program will draw lines example if the user enters an 8 and clicks the sin button 8 jagged looking lines will be drawn the larger the number entered the smoother looking the line can anyone help with this? If it will help any I can post what I already have.
Therefore, posting your code and stating a little clearer would have your project helped anyways, at least Home think so...
Regards,
Hometown
Sorry Here is what I have, What I'm having trouble with is getting it to draw a sine curve ie based on the number wntered that number of lines should be drawn right now I get a straight line across the top. I appreciate any help you might give.
void CProject5View::OnDraw(CDC* pDC)
{
double PI = 3.1415926535;
int count;
int i;
double iSamplesvalue = 300 -(m_iSamples * PI);
pDC->MoveTo(60, 150);
pDC->LineTo(60, 300);
pDC->LineTo(575, 300);
pDC->MoveTo(60, 300);
pDC->LineTo(60, 450);
switch (m_Chart) {
case Sin:
for(i = 0; i < count; i++);
pDC->MoveTo (300, m_iSamples);
pDC->LineTo (60, m_iSamples);
break;
}
}
Well, you need to use i (which is actually your x value) as well as iSamplesvalue (which is actually your y value, and which you have to recalculate inside the loop), both scaled accordingly and converted to integer values, in your LineTo() call. Also, do only one MoveTo() at the beginning, and call only LineTo() for every sample inside your loop.
Just another thing: You should use a more descriptive subject for your post, maybe "Drawing Graph in CView" or something like that. A subject like "Need Help" is far too unspecific and will prevent many people from looking at your thread.
Sorry first time posting here. How would I recalculate my x and y values in the loop. I've not had much practice with graphing. From what you have seen of my code is everything correct?
Not really, as your for loop doesn't do anything (it has no body). You just count a variable i up from 0 to count. After that, you draw one single line with fixed length and position.Quote:
Originally posted by JerryShane
From what you have seen of my code is everything correct?
You should first get a clear idea about what you actually want to do, and jot that down. Probably something like this:
Your code, in contrast, does the following:Code:For every x value from the first value to the last value:
Calculate the y value using sin() or cos()
Draw a line from the last position to the new x/y position
End
Besides from the actual drawing logic (which is missing completely), the rest of your code (which uses the pDC passed in OnDraw() for drawing) is OK.Code:For every i value from 0 to count:
Do nothing
Then draw a Line from 300/m_iSamples to 60/m_iSamples
After you have sufficiently described (in pseudo code) what you actually want to happen, it will be fairly easy to convert that to actual code.
Thanks, but I'm having a little trouble figuring out to plot the x, y values and draw the lines based on the number entered. Also I should mention that I have a switch statement for sin and cosin will my loop and the necessary code to draw the lines be inside or outside the switch statment? I appreciate your help. This is really frustrating.
The switch value just incides on whether you use sin() or cos() to calculate the y value from a given x value. So why should you duplicate the entire looping and drawing code? Of course there are better approaches like using function pointers (in C) or virtual functions (in C++) to provide different plotting functions, but for the moment, you should probably just make the switch statement inside the loop.Quote:
Originally posted by JerryShane Also I should mention that I have a switch statement for sin and cosin will my loop and the necessary code to draw the lines be inside or outside the switch statment?
You are not very specific about what exacltly you're having problems with. As far as I understand from your initial post, the number entered by the user determines how many samples are used to plot the graph, so you should start by dividing the horizontal space avalilable into that number of equidistant x values. How are you proceeding with the pseudo-code for your plotting algorithm?Quote:
Originally posted by JerryShane
Thanks, but I'm having a little trouble figuring out to plot the x, y values and draw the lines based on the number entered.
This is what I have for when the sin button is pressed. am I getting close?
pDC->MoveTo(60, 150);
pDC->LineTo(60, 300);
pDC->LineTo(575, 300);
pDC->MoveTo(60, 300);
pDC->LineTo(60, 450);
for(i = 0; i < count; i++);
switch (m_Chart) {
case Sin:
double iSamplesvalue = 300 -(m_iSamples * 150);
pDC->MoveTo (300, m_iSamples);
pDC->LineTo (60, m_iSamples);
break;
}
}
Unfortunately, not even a little. Basically, you do nothing different than before: Your loop still lacks a body, you still don't do any sin() calculation involving x and y, the code which calculates the step value for x is still missing, the lines you draw still use fixed coordinates (they don't depend in any way on x and y), it is still unclear what you are doing with m_iSamples and what iSamplesvalue is for, why you use the 'i' prefix for a double variable etc.Quote:
Originally posted by JerryShane
This is what I have for when the sin button is pressed. am I getting close?
So I ask you once again (for the third time now) to write down in an informal way what your code is supposed to do - step by step. After that, it will be easier to transform that into working code. But if you don't even have an idea about what your code should be doing, than you won't get any furhter just by trying and guessing. It's like you were trying to build an electronic device by just arbitrarily soldering together a handful of transistors, capacitors etc. You first need to plan what your device is meant to do and how it works, and come up with a circuit diagram. After that, you will know which components you need and how to put them together, following the diagram.
m_Samples is a member variable, and iSampleValue is the text box that the user enters a value into. I'm not the best at math so that is why it is hard for me to figure out how to write the code to calculate the sin/cosin. I know how the program is supposed to function it's just putting that into code that's giving me fits. I appreciate your patience while I figure this out.
I highly doubt that. While m_iSamples is probably an integer DDX variable mapped to your edit control (and hence contains the entered value), iSampleValue is a double variable, and therefore can't be a "text box".Quote:
Originally posted by JerryShane
m_Samples is a member variable, and iSampleValue is the text box that the user enters a value into.
Little math is required to do that, just call the library functions sin() and cos(), respectively. Note however that they expect the angle as radians, so the x values you input should be in the range of something like 0..PI, 0..2PI or the like (depending on how many cycles you want to plot).Quote:
I'm not the best at math so that is why it is hard for me to figure out how to write the code to calculate the sin/cosin.
Thanks I'll be in touch as I work on this. Sorry my bad I was looking at what I have here at work which is different than what I have at home. What I have is a text box with a member variable m_Samples I used m_SampleValues because this book I've got had something similiar to draw lines based on stock amounts entered but it wasn't a sin curve it was just straight lines so I was comparing what was in the book to what I'm trying to do.
How does this look so far?
double PI = 3.1415926535;
int count;
int i;
double angle;
double x, y;
x = pi / 2;
y = sin(x);
double sin_of_angle = sin(angle);
pDC->MoveTo(60, 150);
pDC->LineTo(60, 300);
pDC->LineTo(575, 300);
pDC->MoveTo(60, 300);
pDC->LineTo(60, 450);
switch (m_Chart) {
case Sin:
for(i = 0; i < count; i++);
I don't know why you still keep refusing to depict in pseudo code what you program is supposed to do... :rolleyes:
However, here is what it does so far:
I don't know if that's what you intended, but I don't think so, as it is still very far from anything that would draw a graph. The various values are completely unreleated here. What's the role of i, and what is count? What's the point in using a variable who's value has never been set to anything meaningful for calculating another value?Code:- calculate sin(PI/2) and store it in y
- calculate the sinus of an uninitialized angle variable and
store it in sin_of_angle (which now contains an arbitrary
random value)
- draw a T-shaped coordinate cross
- if Sin was chosen:
- count i up from 0 to count (another uninitialized variable)
- do nothing else with i (it is completely useless, as is the loop)
Code:double PI = 3.1415926535;
int count;
int i;
double angle;
double x, y;
x = pi / 2;
y = sin(x);
//angle = ??? it's not initialized!
double sin_of_angle = sin(angle);
pDC->MoveTo(60, 150);
pDC->LineTo(60, 300);
pDC->LineTo(575, 300);
pDC->MoveTo(60, 300);
pDC->LineTo(60, 450);
//who is m_Chart ???
switch (m_Chart) {
case Sin:
//who is count. count = ??? it's not initialized
//what do you do with this for??? nothing i see.
for(i = 0; i < count; i++);
are you aware of what you are supposed to do? i think not!
why do you keep ignoring gstercken advices?
do you know how to write pseudocode? if yes, then do it.
please clarify all these things to yourself and to us and then you might get useful help.
okay here is what it's supposed to do. I've not written psuedocode before.
-Draw a graph
-enter number to calculate
- if either the sin or cos button is pressed
-calculate the value entered and draw lines based on the number entered.
OK, now let's have a look at what you specified. First of all, you state that you start by drawing a graph, but I assume that you just mean drawing the coordinate system (as for drawing the graph, you need the number entered in the second step).
Step two, "enter a number to calculate" is already done by the DDX mechanism, I think it is safe to assume that you already have the number (more specifically, the number of samples to be used to draw your graph, that's important) in m_iSamples.
Step three describes the reaction to clicking one of the buttons. You didn't post the code, but I assume that the handlers for the two buttons just set the value of m_Chart to Sin or Cos, respectively, and invalidate the view to have it redrawn, so we can fully concentrate on step 4, the part actually missing from your implementation so far: "calculate the value entered and draw lines based on the number entered". Now that's a little vague, and you should probably break it down further.
You are actually describing two large, distinct steps here:
1. calculate the value entered
2. draw lines based on the number entered
As to 1.: The value entered is already in m_iSamples, so it doesn't need to be calculated. What do you need to calculate instead, and how does this depend on the number entered?
As to 2.: This step is described very vaguely, so you should try to further break it down into several steps. What lines do you want to draw, and how do they depend on the number entered? Where are the sin and cos in this description, and where is the loop?
I'll break it down even further once I get home to exactly what I am trying to accomplish. Oh yea I'll post the code for m_Chart and more importantly what it is.
Okay I'll break it down further.
-use the MFC app wizard
-add variables and message handlers
-user enters number of samples to draw example 8
-user presses the sine button
-use 8 lines to draw the sine curve.
-graph the sine and/or cosine function
-x axis will start at 0 and end at 2 p radian measures
-y axis will run from 1 to -1
- define p as double 3.1415926535
- scale the x,y values to match the display
- use m_chart to determine which button was selected
this is what I have to create the m_chart variable
class CProject5View : public CFormView
{
protected: // create from serialization only
CProject5View();
DECLARE_DYNCREATE(CProject5View)
enum {Sin, Cos} m_Chart;
Well, let's see how to go about this...
Now, what you listed so far is not a further breakdown of the "draw lines" step, but rather a collection of various items. Note that pseudocode should describe what the program (or rather a part of it) is supposed to do, not what you should do. The following items, however, describe what you have to do, making it sound much like a homework assignment... ;):
-use the MFC app wizard
-add variables and message handlers
The next two items, OTOH, describe a possible scenario of what the user of your program might do, not what the program does:
-user enters number of samples to draw example 8
-user presses the sine button
The following items, in turn, don't describe what happens, but are rather constraints to be applied. They have nothing to do with pseudocode, but are important nonetheless:
-x axis will start at 0 and end at 2 p radian measures
-y axis will run from 1 to -1
- define p as double 3.1415926535
Finally, these items are actually part of the process of drawing the graph:
- scale the x,y values to match the display
- use m_chart to determine which button was selected
- graph the sine and/or cosine function
- use 8 lines to draw the sine curve.
The first is very important and was missing from your description so far. It brings us to the fact that you are actually dealing with two coordinate spaces here:It should be obvious that you need the screen coordinate limits for drawing the axes and for plotting the graph, so you should better define them as constants (we could use 'S' to denote them as being Screen coordinates):
- The logical coordinates, which range from 0 to 2*PI (x) and -1 to 1 (y) as described above, with the origin at (0,0)
- The screen or window coordinates used for drawing, which are pixels in your case. Note that the way you draw the axes imply that screen coordinates range from 60 through 575 for x and from 150 to 450 for y, the origin being at (60,300).
Sx0 = 60 (x origin)
SxExt = 515 (extent of the x axis)
Sy0 = 300 (y origin)
SyExt = 150 (extent of the y axis)
From these, we can derive additional useful constants to be used in drawing:
SxMin = Sx0 (minimal x screen value)
SxMax = Sx0 + SxExt (maximal x screen value)
SyMin = Sy0 + SyExt (minimal y screen value)
SyMax = Sy0 - SyExt (maximal y screen value)
Note how the '+' and '-' signs are used to calculate SyMin and SyMax, this is because the y axis in screen coordinates extends downward (as often in computer graphics). Now casting that into C++ code is pretty straightforward. As you started using the 'i' prefix for integer variables, we will continue doing so:
Using those constants, you can now rewrite the code for drawing the axes like this:Code:const int iSx0 = 60; // x origin
const int iSxExt = 515; // y origin
const int iSy0 = 300; // extent of the x axis
const int iSyExt = 150; // extent of the y axis
const int iSxMin = iSx0; // minimal x screen value
const int iSxMax = iSx0 + iSxExt; // maximal x screen value
const int iSyMin = iSy0 + iSyExt; // minimal y screen value
const int iSyMax = iSy0 - iSyExt; // maximal y screen value
Note how this makes much clearer what your MoveTo / LineTo calls actually do. Also, if you want to change the position or size of the screen coordinate space later, you just need to modify the base constants. You could even make them variables in the future, and automatically scale the coordinate space depending on the current windwow size if you like.Code:// Draw X axis:
pDC->MoveTo(iSx0, iSy0);
pDC->LineTo(iSxMax, iSy0);
// Draw Y axis:
pDC->MoveTo(iSx0, iSyMax);
pDC->LineTo(iSx0, iSyMin);
Next, you need to plot the graph. Think a moment about what 'plotting a graph' actually means: Taking a series of x values, calculating the corresponding y value for every x value, and drawing a line to the point given by (x, y). Now, how do you get a 'series of x values'? Probably by using a loop which starts at some x value and increments that by some step value until the maximal x value is reached. Now, in your case, you have three concurring parameters which could possibly define the range of x values: The logical coordinate space (0 through 2*pi), the screen coordinate space (iSxMin through iSxMax) or the sample count (0 through 8, note that you need 9 samples to draw 8 lines). Each of the three could be used as the loop counter, giving you the following three options to build the loop:Now which option you choose is up to you, however, due to possible double / integer conversion effects, I would suggest you use option C (without elaborating further on that here).
- Your loop counter is a real number starting at 0 and ending a 2*PI. The increment to be used in each iteration is 2*PI divided by the number of samples. In each iteration, calculate the sin (or cos) from the x value, transform logical x and y values to screen coordinates, and draw the line.
- Your loop counter is an integer variable representing the screen x coordinate, starting at iSxMin and ending at iSxMax. The increment to be used is iSxExt divided by the number of samples. In each iteration, calculate the logical x value from the screen x value. Calculate the logical y value as sin(x) or cos(x), transform it to screen coordinates, and draw the line.
- Your loop counter is the sample index, starting at 0 and ending at m_iSamples. For each sample, you calculate the logical x value for that sample, and the corresponding y value using sin() or cos(). Then you transform them to screen coordinates and draw the line.
Now, having paved the way so far I would like to leave that task to you: Write the loop as pinpointed in option C. Use the constants defined above to convert between sample index, logical coordinates and screen coordinates. If you have questions, ask.
wow, what an explanation !!!
i wish someone would have thought me like this when i first started doing stuff in C++ :D :)
It's not a homework assignment I have this book and it's one of the excercise problems. I wanted to try and do.Yea thanks for the explanation hopefully I can get this it's rather frustrating. I will ask you have been most hopefull.
Well, it shouldn't be frustrating. It's a classical programming task which is fairly straightforward to implement - the important thing is to analyze the problem correctly, that is, to get a clear and detailed idea of what should happen, and then come up with a likewise detailed solution of how it should happen. I hope the above helps you to get the point.Quote:
Originally posted by JerryShane
Yea thanks for the explanation hopefully I can get this it's rather frustrating.
Yes it does thsnks for your help I'll be in touch if I have any more questions. You're right it shouldn't be frustrating.