matlab plot function

Apr 2010
23
0
Code:
x1=-10:.1:10;
y1=exp(x1) - (7*x1);
plot(x1,y1);
The graph that i get looks very wrong

How can i resolve this issue

Please help.
 

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Laurent

MHF Hall of Honor
Aug 2008
1,174
769
Paris, France
Code:
x1=-10:.1:10;
y1=exp(x1) - (7*x1);
plot(x1,y1);
The graph that i get looks very wrong

How can i resolve this issue

Please help.
The graph IS correct. But give a look at the scale on the vertical axis... Problem is that for x=10, \(\displaystyle \exp(x)\) is huge, so that we can't even distinguish \(\displaystyle -70\) (which would be the value for x=-10, approx.) from 0.

"Solution" is to adjust the extent of the values x is assumed to take: choose x1=-10:.1:5 instead, for instance.
 
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Apr 2010
23
0
Well i didn't focus on the shape of the graph for positive values for x

For negative values of x the graph looks very very wrong

at x values lesser than zero the graph should go in the upward direction but the graph that mat-lab gives me lies on the x axis.

Please help me.
 

Laurent

MHF Hall of Honor
Aug 2008
1,174
769
Paris, France
Well i didn't focus on the shape of the graph for positive values for x

For negative values of x the graph looks very very wrong

at x values lesser than zero the graph should go in the upward direction but the graph that mat-lab gives me lies on the x axis.
That's what I said. Matlab scales the axes so that the plot fits inside the window. The values for positive x are huge, so that Matlab has to choose a very large scale (I mean, which grows very quickly). On the other hand, on such a scale, the positive slope for negative x looks horizontal because it is not very steep. Make the change I recommended, and then maybe you'll get what I mean.
 
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