SVG xy scatter graph of mathematical relationships
grid
axes
data points
text layers
Current versus voltage: linear relationship
y-intercept = 0: use LINEST
x-axis: i (amperes)
y-axis: V (voltage) y-axis labels
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
x-axis labels
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
grid
axes
data points
text layers
Linear, y-intercept ≠ 0
Use SLOPE and INTERCEPT
x-axis: woddles
y-axis: widdles y-axis labels
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
x-axis labels
0.0
1.0
2.0
3.0
4.0
5.0
7.0
7.0
SVG xy scatter graph depicting non-linear relationshp
grid
axes
data points
text layers
Non-linear mathematical relationship
Smooth curve
x-axis: wubbles
y-axis: wibbles y-axis labels
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
x-axis labels
0.0
1.0
2.0
3.0
4.0
5.0
7.0
7.0
grid
axes
data points
text layers
No mathematical relationship
No pattern, no alignment
x-axis: woddles
y-axis: widdles y-axis labels
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
x-axis labels
0.0
1.0
2.0
3.0
4.0
5.0
7.0
7.0
Mathematical relationship analysis decision tree
Does the data form a straight line or roughly close to a straight line?
Yes
No
Arrow
Arrow
First analysis conclusion:
There is a mathematical relationship.
Second conclusion:
The data is linear.
Is the y-intercept zero or close to zero?
Yes
No
Arrow
Arrow
Third analysis
conclusion:
The y-intercept
is zero.
Use LINEST(y;x;0)
to find slope.
Third analysis
conclusion:
Linear.
Use SLOPE(y;x)
INTERCEPT(y;x)
Does the data form a smooth curve
or roughly close to a smooth
curve?
Yes
No
Arrow
Arrow
First analysis conclusion:
There is a mathematical
relationship.
Second conclusion:
The mathematical
relationship is non-linear.
First and:
only
conclusion:
NO
mathematical
relationship.
The functions provided in the above chart are specified in more detail below. The format shown is the OpenOffice.org Calc format. If using Excel, substitute commas for the the semi-colons.
The first function finds the slope of a line with the y-intercept equal to 0
=LINEST(y-data;x-data;0)
The following two functions calculate the slope and intercept for any linear relationship.
=SLOPE(y-data;x-data)
=INTERCEPT(y-data;x-data)
Physci spring 2008 •
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