How to get the area under the curve

[多多]

Hello, 
Such as under the map, in theory, the area under the white line is 0.5 * 1 = 0.5
But integral operator out of the area is  0 , it's seems to be offset?
How can i modify my vi?

thanks~

[altenbach]

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多多 wrote:

Such as under the map, in theory, the area under the white line is 0.5 * 1 = 0.5

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No, the area under the white line is zero, because half of the white line is at -1. If you would add 1 to your data, you would get an area of 1.

If you want an area of 0.5, you should trim your data so it ends at time=0.5.

It really depends what you actually want. Please explain.

[多多]

sorry ,the describe 0.5 * 1 = 0.5 is error .

(1) I want the area is 0.5(the orizontal axis length) x 2(the vertical axis length) =1

     so, i have to add 1 to my data by myself ?

(2) Can I change the horizontal time axis coordinates at front panel  Waveform Graph

     (original 0 to 1)=>(0 to 1.4E-6) ?

THANKS~

[johnsold]

Take the absolute value of the signal before integrating.  This will  effectively ignore the sign of the signal. When you do this the signal in your example will be a constant at +1 for the entire duration.

Lynn

[MKirk]

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@多多 wrote:

sorry ,the describe 0.5 * 1 = 0.5 is error .

(1) I want the area is 0.5(the orizontal axis length) x 2(the vertical axis length) =1

     so, i have to add 1 to my data by myself ?

(2) Can I change the horizontal time axis coordinates at front panel  Waveform Graph

     (original 0 to 1)=>(0 to 1.4E-6) ?

THANKS~

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(1) According to your VI, you want a 1Hz square wave with a 50% duty cycle. If this is true, and you want the first half of your square wave to have an area of 1, then you will either have to add an offset of 1, or set the amplitude of the square wave to 2 (by default the amplitude is 1).

(2) Yes, you can change the time-axis coords. Left-click the number "1" on the Time-axis, then enter whatever number you want. Or, right-click the graph, select properties, switch to the "Scales" tab, then change the Maximum/Minimum values.

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Matt Kirk

Inventor of ImageJVI

[crossrulz]

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@多多 wrote:

sorry ,the describe 0.5 * 1 = 0.5 is error .

(1) I want the area is 0.5(the orizontal axis length) x 2(the vertical axis length) =1

     so, i have to add 1 to my data by myself ?

(2) Can I change the horizontal time axis coordinates at front panel  Waveform Graph

     (original 0 to 1)=>(0 to 1.4E-6) ?

THANKS~

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(1)  Do you also want the second half of the waveform to be 0?  If so, set the offset of the waveform to 1.

(2)  The autoscaling is kicking in here.  What you want to do is increase the waveform frequency to something like 715kHz (or higher).  You may have to increase the Sampling Frequency (part of the sampling info cluster) in order to accommodate this.