[General Topics] Skyica:
Graphing Calculator + Math​

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This app stands out with very good (although not optimal) 2D graphing, quite good 3D graphing, and some useful user interface features that are missing from most or all other apps.

Its calculation capabilities are quite limited however (e.g., simplifications are often not done, more complicated equations cannot be solved, no symbolic integration).

While the user interface has very useful features, it also has significant inconveniences.

The user manual is comprehensive and excellent for people just learning math.

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Numeric and symbolic calculation​

Symbolic computation essentials:

Bad Limited calculation with exact values (e.g., logarithms are always evaluated numerically)

Bad Limited simplification, e.g. e^(x+1)/e is not simplified

(however, it simplifies 2x/(x^2-1)-1/(x-1) which Hiper does not simplify)

Feature Polynomials are displayed in both expanded and factored form

Equation solving:

Bad Equations involving periodic functions cannot be solved symbolically

Bad Equations with parameter variables cannot be solved

Feature Inequalities

Differentiation and integration

Bad For symbolic differentiation the simplification problems are an issue, e.g., the derivative of ln(√x) is given as 1/(2x^(1/2)* √x) instead of 1/(2x).

Missing No symbolic integration

Other calculus and analysis:

Bad Sums and products of sequences only numeric

Bad Limits only numeric

Statistics and probability

Missing Only 1 variable statistics, no data editor

Missing Only linear regression

Missing No bit-operations

2D and 3D graphing​

Missing In 3D, only one graph can be shown at a time

Feature Multiple workspaces

Graph types:

Feature Implicit plots in 2D and 3D.

Good Also more complicated implicit surfaces can be drawn, e.g. 4*(x^2+y^2+z^2)+16*x*y*z = 1 (Cayley's surface), which GeoGebra does not draw. However, Scientific Calculator by Philip Stephens draws implicit surfaces in much better quality.

Display

3D: Perspective projection only

3D surfaces display: Wireframe only

Navigation

Feature Independent scale of axes in 2D, well implemented.

Missing No simultaneous pan and zoom with 2 fingers

3D: Complete navigation, but not very efficient (and unusual)

Analysis

Good Tracing is well implemented, also “reverse” tracing with a horizontal line

Environment and user interface​

Variables and functions:

Feature Custom-named variables

Feature User-defined functions that can be used in numeric and symbolic calculations

Input and output

Bad Much functionality is hidden behind unlabeled keys (e.g., for integrals and derivatives, long-tap the x^n key!)

Missing Input of expressions in linear notation (simultaneously, they are displayed in textbook notation, which can also be tapped to position the cursor). The advantage over most other calculators is that parts of expressions can be selected and copied at least in this way.

Bad Very limited undo

Feature It has a limited “notebook interface” where elements can be rearranged and comments can be added.

Feature Multiple workspaces, however all variables and functions are shared

Adaption and customization:

The keys are quite small for phones (the keyboard can “resized” to fewer, larger keys, but then important functionality is missing).

Bad User interface does not adapt to different screen sized and orientations

Documentation and source​

Good The user manual is really comprehensive and excellent for people just learning math, available online and as PDF.