# Plotting a line using one point and a slope in the loglog scale

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Alex on 29 Nov 2022
Commented: VBBV on 29 Nov 2022
I am trying to plot a line in the loglog scale using a given point and a slope but the graph(attached) that I am getting is not correct. This is what I have tha gives me the graph attached.
x = (25081:1000:10000000);
m = -3.62;
x1 = log(25081);
y1 = log(3.046*10^-16);
y = m*(x-x1)+ y1;
loglog(x, y)

VBBV on 29 Nov 2022
x = (25081:1000:10000000);
m = -3.62;
x1 = 25081; % use coordninate
y1 = 3.046e-16;
y = m*(x-x1)+ y1
y = 1×9975
1.0e+07 * 0.0000 -0.0004 -0.0007 -0.0011 -0.0014 -0.0018 -0.0022 -0.0025 -0.0029 -0.0033 -0.0036 -0.0040 -0.0043 -0.0047 -0.0051 -0.0054 -0.0058 -0.0062 -0.0065 -0.0069 -0.0072 -0.0076 -0.0080 -0.0083 -0.0087 -0.0091 -0.0094 -0.0098 -0.0101 -0.0105
loglog(x, abs(y)) % log of negative number are not defined VBBV on 29 Nov 2022
Since the slope is negative , the y vector will be negative. instead you can use semilogx
x = (25081:1000:10000000);
m = -3.62;
x1 = 25081; % use coordninate
y1 = 3.046e-16;
y = m*(x-x1)+ y1
y = 1×9975
1.0e+07 * 0.0000 -0.0004 -0.0007 -0.0011 -0.0014 -0.0018 -0.0022 -0.0025 -0.0029 -0.0033 -0.0036 -0.0040 -0.0043 -0.0047 -0.0051 -0.0054 -0.0058 -0.0062 -0.0065 -0.0069 -0.0072 -0.0076 -0.0080 -0.0083 -0.0087 -0.0091 -0.0094 -0.0098 -0.0101 -0.0105
semilogx(x, y) % considering the slope direction ### Categories

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